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A

Angular Frequency

Angular frequency (also referred to by the terms angular speed, radial frequency, circular frequency, orbital frequency, radian frequency and pulsatance) is a scalar measure of rotation rate.

Angular Diameter

The angular diameter or apparent size is an angular measurement describing how large a sphere or circle appears from a given point of view.

Area Moment of Inertia of an Annulus about a Centroidal Axis

The second moment of area, also known as moment of inertia of plane area, area moment of inertia or second area moment, is a geometrical property of an area that reflects how its points are distributed with regard to ...

Abbe Number

The Abbe number, also known as the V-number or constringence of a transparent material, is a measure of the material's dispersion (the variation of refractive index versus wavelength), with high values of V indicating...

Acceleration Number

The acceleration number characterizes acceleration flow.

Accelerating Frequency

Fluid dynamic accelerating frequency

Adiabatic Process Equations for an Ideal Gas

An adiabatic process is one that occurs without transfer of heat or matter between a thermodynamic system and its surroundings. Energy is transferred only as work.

Albedo

Albedo is a measure for reflectance or optical brightness.

Alfvén Number

The Alfvén number describes the relative scale for phenomena within an Alfvén wave, a type of magnetohydrodynamic wave in which ions oscillate in response to a restoring force provided by an effective tension on the m...

Allometry Relation for Tree-Trunk Diameter and Height

Tree allometry establishes quantitative relations between tree-trunk diameter and height.

Angle of View

The angle of view describes the angular extent of a given scene that is imaged by a camera in the vertical and horizontal directions.

Angle Subtended

The angle formed between the bottom and top of an object at a distance from the observer.

Angular Velocity under Constant Angular Acceleration

The angular velocity of a body is the rate of change of its angular displacement with respect to time.

Angular Velocity by Initial and Final Values

The angular velocity of a rotating body is defined as the rate of change of angular displacement.

Angular Momentum of a Rigid Body

Angular momentum is the rotational analog of linear momentum. For a rigid body, it equals the cross-product of the particle's position vector (relative to some origin) and its momentum vector.

Anti-Knock Index

The Anti­Knock Index (AKI) or posted octane number (PON) is the headline octane rating shown on the pump in Canada, the United States, Brazil and some other countries.

Archimedes's Principle

Any object, wholly or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object.

Archimedes Number

The Archimedes number is used to determine the motion of fluids due to density differences. It is a dimensionless number defined as the ratio of external forces to internal viscous forces.

Arc Length on a Circle

The arc length on a circle is the length of arc, or segment, of the circle.

Area Moment of Inertia of a Regular Pentagon about a Centroidal Axis

The second moment of area, also known as moment of inertia of plane area, area moment of inertia or second area moment, is a geometrical property of an area that reflects how its points are distributed with regard to ...

Area Moment of Inertia of a Regular Hexagon about a Centroidal Axis

The second moment of area, also known as the moment of inertia of plane area, area moment of inertia or second area moment, is a geometrical property of an area that reflects how its points are distributed with regard...

Area Moment of Inertia of a Quarter Disk about a Centroidal Axis

The second moment of area, also known as moment of inertia of a plane area, area moment of inertia or second area moment, is a geometrical property of an area that reflects how its points are distributed with regard t...

Area Moment of Inertia of a Half-Disk about a Centroidal Axis

The second moment of area, also known as the moment of inertia of a plane area, area moment of inertia or second area moment, is a geometrical property of an area that reflects how its points are distributed with rega...

Area Moment of Inertia of a Filled Triangle about a Centroidal Axis

The second moment of area, also known as moment of inertia of plane area, area moment of inertia or second area moment, is a geometrical property of an area that reflects how its points are distributed with regard to ...

Area Moment of Inertia of a Filled Trapezoid about a Centroidal Axis

The second moment of area, also known as moment of inertia of plane area, area moment of inertia or second area moment, is a geometrical property of an area that reflects how its points are distributed with regard to ...

Area Moment of Inertia of a Filled Rectangle about a Centroidal Axis

The second moment of area, also known as moment of inertia of a plane area, area moment of inertia or second area moment, is a geometrical property of an area that reflects how its points are distributed with regard t...

Area Moment of Inertia of a Disk about a Centroidal Axis

The second moment of area, also known as the moment of inertia of a plane area, area moment of inertia or second area moment, is a geometrical property of an area that reflects how its points are distributed with rega...

Area of a Regular n-Gon

A regular n-gon is a plane figure that is bounded by a chain of n straight line segments of equal length closing in a loop to form a closed polygonal chain.

Arrhenius Number

The Arrhenius equation is a formula for the temperature dependence of reaction rates. The Arrhenius number is the exponent for that equation.

Atkinson Cycle

The Atkinson-cycle engine is a type of internal combustion engine invented by James Atkinson in 1882. The Atkinson cycle is designed to provide efficiency at the expense of power density, or total power extracted per ...

Atwood Number

The Atwood number is a dimensionless number in fluid dynamics used in the study of hydrodynamic instabilities in density-stratified flows.

Average Speed by Displacement

The speed of an object is the rate of change of its position.

Average Angular Velocity by Displacement

The angular velocity of a rotating body is defined as the rate of change of angular displacement.

Avogadro's law states that equal volumes of all gases, at the same temperature and pressure, have the same number of molecules. For a given mass of an ideal gas, the volume and amount (moles) of the gas are directly p...

Axial Member Deformation

Axial member deformation is the deformation of the support due to a load along the axis of support.

B

Bond Clean Price between Regular Coupon Payments

The clean price of a bond is the value of a bond, excluding accrued interest since issue or the most recent coupon payment.

Bond Clean Price between Coupon Payments with a Short First Coupon

The clean price of a bond is the value of a bond, excluding accrued interest since issue or the most recent coupon payment.

Bond Dirty Price between Regular Coupon Payments

The dirt price of a bond is the value of a bond, including accrued interest since issue or the most recent coupon payment.

Bond Dirty Price between Coupon Payments with a Short First Coupon

The dirt price of a bond is the value of a bond, including accrued interest since issue or the most recent coupon payment.

Bagnold Number

The Bagnold number is the ratio of grain collision stresses to viscous fluid stresses in a granular flow with interstitial Newtonian fluid.

Barometric Formula for Pressure

The barometric formula (also called the exponential atmosphere or isothermal atmosphere) is a formula used to model how the pressure of the air changes with altitude.

Barometric Formula for Density

The barometric formula (also called the exponential atmosphere or isothermal atmosphere) is a formula used to model how the density of the air changes with altitude.

Baseball Weighted On-Base Average

The weighted on-base average measures a player's overall offensive contribution per plate appearance.

Baseball Walks Plus Hits per Inning

The walks plus hits per inning pitched is a sabermetric measurement of the number of baserunners a pitcher has allowed per inning pitched. It reflects a pitcher's propensity for allowing batters to reach base; therefo...

Baseball Slugging Percentage

Slugging percentage (SLG) is a measure of the batting productivity of a hitter,defined as the total bases divided by the number of at bats.

Baseball Secondary Average Formula

Secondary average is a baseball statistic that measures the sum of extra bases gained on hits, walks and stolen bases (less times caught stealing) depicted per at bat. It is a sabermetric measurement of hitting perfor...

Baseball Runs Created

Runs created is a baseball statistic used to estimate the number of runs a hitter contributes to his team.

Baseball Range Factor

Range factor is a measurement of a player's fielding, defined as the number of times a player is involved in making an out divided by innings played.

Baseball Pythagorean Win Expectancy

Pythagorean Win Expectancy is an estimate of how many games a team should win based upon runs scored and runs allowed.

Baseball On-Base Percentage Plus Slugging Percentage

On-Base Plus Slugging is a single statistic that shows both a batter's ability to get on base and to hit for power, defined as on-base percentage plus slugging percentage.

Baseball Isolated Power

Isolated Power, or ISO, is a sabermetric computation used to measure a batter's raw power by showing how many extra bases a player averages per at bat, defined as slugging percentage minus batting average.

Baseball Game Score

Game score in baseball is a metric of the strength of a pitcher in a game with a starting value of 50.

Baseball Earned Run Average

The earned run average is the average number of allowed earned runs normalized to the length of a full game.

Baseball Batting Average on Balls in Play

The batting average on balls in play is the ratio of hits excluding home runs to at bats excluding strikeouts and homeruns, but including sacrifice flies.

Usage rate estimates the percentage of a team's possessions a player uses while on the floor.

The true shooting percentage is the shooting percentage adjusted for three-pointers and free throws, and measures a player's efficiency at shooting the ball.

Field goal percentage in basketball is the ratio of field goals made to field goals attempted.

The effective field goal percentage is a statistic that adjusts field goal percentage to account for the fact that three-point field goals count for three points, while field goals only count for two points.

The assist rate estimates the percentage of a team's possessions a player assists on while on the floor.

Beale Number

The Beale number is a parameter that characterizes the performance of Stirling engines and is often used to estimate the power output of such engines.

Beer–Lambert Law with Napierian Absorbance

The Beer–Lambert law relates the attenuation of light to the properties of the material through which the light is traveling.

The Beer–Lambert law relates the attenuation of light to the properties of the material through which the light is traveling.

Bejan Number for Heat Transfer

The Bejan number is the dimensionless pressure drop along a channel of length L.

Bell Coleman Cycle

The Bell Coleman cycle is a Brayton cycle driven in reverse, via network input, with air as the working fluid. Also called a gas refrigeration cycle, its purpose is to move heat, rather than produce work.

Bench Stepping

The step count is the number of steps completed by exercising with bench stepping.

Benjamin Graham Formula

The Benjamin Graham formula is an intrinsic value formula used to quickly determine how rationally priced stocks were.

Bernoulli's Energy Equation

Bernoulli's energy equation derives from Bernoulli's principle, which states that an increase in the speed of a fluid across a surface will result in a decrease of the force exerted (pressure) on that surface, or a de...

Bethe Formula

The Bethe formula describes the mean energy loss per distance traveled of swift-charged particles (protons, alpha particles, atomic ions) traversing matter (or, alternatively, the stopping power of the material).

Bicycling Time by Pace

Pace is the time it takes to cover a certain distance.

Bicycling Distance by Speed

Bicycling distance equals speed times time.

Bingham Compression Number

The Bingham compression number expresses the state of a semisolid Bingham material if compressed.

Biot Number

The Biot number is a dimensionless quantity used in heat transfer calculations. It determines whether or not the temperatures inside a body will vary significantly in space, while the body heats or cools over time, fr...

Birthday Problem Approximation

The birthday problem, or birthday paradox, concerns the probability that, in a set of n randomly chosen people, some pair of them will have the same birthday.

Blackbody Luminosity of a Sphere

The blackbody luminosity for a sphere is the total amount of energy emitted by a sphere with uniform temperature in thermal equalibrium with its surroundings.

Black Hole Temperature

The temperature of a black hole is calculated as if the electromagnetic radiation it emits came from a blackbody.

Black Hole Surface Gravity

The surface gravity of a black hole with a static Killing horizon is the acceleration, as exerted at infinity, needed to keep an object at the horizon.

The total radiated power of a black hole comes from Hawking radiation, caused by quantum effects near the event horizon.

A black hole will eventually disappear (or evaporate) due to escaping Hawking radiation. The lifetime of a nonrotating, noncharged Schwarzschild black hole can be derived from the formulas for the Schwarzschild radius...

The event horizon of a black hole is a boundary in spacetime beyond which events cannot affect an outside observer.

Black Hole Event Horizon Area with Charge

An event horizon is a boundary in spacetime beyond which events cannot affect an outside observer.

Black Hole Event Horizon Area with Angular Momentum and Charge

An event horizon is a boundary in spacetime beyond which events cannot affect an outside observer.

Black Hole Event Horizon Area with Angular Momentum

An event horizon is a boundary in spacetime beyond which events cannot affect an outside observer.

Black Hole Event Horizon Area

An event horizon is a boundary in spacetime beyond which events cannot affect an outside observer.

Black Hole Entropy

The entropy of a black hole is derived from its effective temperature. The temperature of a black hole is calculated as if the electromagnetic radiation it emits came from a blackbody.

Blasius Skin Friction

A Blasius boundary layer describes the steady two-dimensional laminar boundary layer that forms on a semi-infinite plate, which is held parallel to a constant unidirectional flow. Skin friction is friction between the...

Blasius Displacement Thickness

A Blasius boundary layer describes the steady two-dimensional laminar boundary layer that forms on a semi-infinite plate, which is held parallel to a constant unidirectional flow.

Blasius Boundary Layer Thickness

A Blasius boundary layer describes the steady two-dimensional laminar boundary layer that forms on a semi-infinite plate, which is held parallel to a constant unidirectional flow.

Blood Glucose Level from Mean Plasma Glucose Molarity

The blood sugar concentration or blood glucose level is the amount of glucose (sugar) present in the blood of a human or animal.

Blood Glucose Level from Mean Plasma Glucose

The blood sugar concentration, or blood glucose level, is the amount of glucose (sugar) present in the blood of a human or animal.

Bodenstein Number with Thermal Diffusivity

The Bodenstein number, a dimensionless number that is often used to describe axial mixing in so-called axial-dispersion models for tubular reactors. It represents the ratio between the convective transport to the tran...

Bodenstein Number with Thermal Conductivity

The Bodenstein number, a dimensionless number that is often used to describe axial mixing in so-called axial-dispersion models for tubular reactors. It represents the ratio between the convective transport to the tran...

Body Mass Index

The body mass index (BMI), or Quetelet index, is a value derived from the mass (weight) and height of an individual.

Bond Number

The Bond number, or Eötvös number, is a dimensionless number measuring the importance of gravitational forces compared to surface tension forces, and is used to characterize the shape of bubbles or drops moving in a s...

Bose–Einstein Distribution for Non-interacting Bosons

The Bose­Einstein distribution describes the occupancy of an energy state within a Bose­Einstein condensate.

Bose–Einstein Condensation Temperature for Noninteracting Bosons Using Volume

The Bose–Einstein condensation temperature is the temperature at which a free Bose gas transitions to a Bose–Einstein condensate. Under such conditions, a large fraction of bosons occupy the lowest quantum state, at w...

Bose–Einstein Condensation Temperature for Noninteracting Bosons Using Pressure

The Bose–Einstein condensation temperature is the temperature at which a free Bose gas transitions to a Bose–Einstein condensate. Under such conditions, a large fraction of bosons occupy the lowest quantum state, at w...

Bose–Einstein Condensation Temperature for Noninteracting Bosons Using Number Density

The Bose–Einstein condensation temperature is the temperature at which a free Bose gas transitions to a Bose–Einstein condensate. Under such conditions, a large fraction of bosons occupy the lowest quantum state, at w...

Boussinesq Number

The Boussinesq number is a dimensionless number representing the square root of the ratio of inertia force to gravitational force.

Boussinesq Approximation Parameter Using Fluid Densities

The Boussinesq approximation is used in the field of buoyancy-driven flow (also known as natural convection). It ignores density differences except where they appear in terms multiplied by the acceleration due to grav...

Boussinesq Approximation Parameter Using Approximated Gravitational Acceleration

The Boussinesq approximation is used in the field of buoyancy-driven flow (also known as natural convection). It ignores density differences except where they appear in terms multiplied by the acceleration due to grav...

Boyle Number

The Boyle number expresses the ratio between the thermodynamic temperature of Boyle's point and the critical temperature.

Boyle's Law

The absolute pressure exerted by a given mass of an ideal gas is inversely proportional to the volume it occupies if the temperature and amount of gas remain unchanged within a closed system.

Bragg's Law

Bragg's law specifies which angles possess coherent and incoherent scattering from a crystal lattice.

Braking Torque

The braking torque is the torque required to maintain a constant motor speed and power.

Brayton Cycle

The Brayton cycle is a thermodynamic cycle that describes the workings of a constant-pressure heat engine.

Brewster's Angle

Brewster's angle is an angle of incidence at which light with a particular polarization is perfectly transmitted through a transparent dielectric surface, with no reflection.

Brinell Hardness

The Brinell scale characterizes the indentation hardness of materials through the scale of penetration of an indenter, loaded on a material test piece.

Brinkman Rheological Number

The Brinkman number is a dimensionless number related to heat conduction from a wall to a flowing viscous fluid, commonly used in polymer processing.

Brinkman Number

The Brinkman number is a dimensionless number related to heat conduction from a wall to a flowing viscous fluid, commonly used in polymer processing.

Brownell–Katz Number by Viscosity

The Brownell–Katz number is a combination of capillary number and Bond number.

Brownell–Katz Number by Bond Number

The Brownell–Katz number is a combination of capillary number and Bond number.

Bulk Concentration

The bulk concentration describes the ratio of suspended particles to the fluid as a whole.

C

Cyclotron Frequency

A cyclotron is a type of particle accelerator in which charged particles accelerate outward from the center along a spiral path. The particles are held to a spiral trajectory by a static magnetic field and accelerated...

Cable Capacitance

Cable capacitance refers to the capacitance of a single core cable.

Capacitor Reactance Formula

Capacitor reactance is the opposition of a capacitor to a change in current or voltage.

Capacitor Energy Using Charge and Voltage

The energy stored in a capacitor depends on the charge and voltage difference across the capacitor.

Capacitor Energy Using Capacitance and Voltage

The energy stored in a capacitor depends on the charge and voltage difference across the capacitor.

Capacitor Energy Using Capacitance and Charge

The energy stored in a capacitor depends on the charge and voltage difference across the capacitor.

Capacitance of Parallel Plates

A capacitor is a passive, two-terminal electrical component that stores electrical energy in an electric field. In a parallel plate capacitor, the capacitance builds up between two closely spaced parallel plates.

Capacitance between Two Parallel Cylinders

A capacitor is a passive, two-terminal electrical component that stores electrical energy in an electric field. In the case of two parallel cylinders, the capacitance builds up between two parallel cylinders of the sa...

Capacitance between Two Concentric Spheres

A capacitor is a passive, two-terminal electrical component that stores electrical energy in an electric field. In the case of two concentric spheres, the capacitance builds up between the inner surface of the outer s...

Capacitance

Capacitance is the ability of a body to store an electric charge, and equals the charge required to cause unit potential difference in a conductor.

Capillary Number

The capillary number represents the relative effect of viscous forces versus surface tension acting across an interface between a liquid and a gas, or between two immiscible liquids.

Capillary Action

Capillary action is the ability of a liquid to flow in narrow spaces without the assistance of, or even in opposition to, external forces like gravity.

Capital Recovery Factor

A capital recovery factor is the ratio of a constant annuity to the present value of receiving that annuity for a given length of time.

Capital Asset Pricing Model

The capital asset pricing model is a model used to determine a theoretically appropriate required rate of return of an asset, to make decisions about adding assets to a well-diversified portfolio.

Carnot Cycle for a Refrigerator

The Carnot cycle is a theoretical thermodynamic cycle conducted on an ideal gas consisting of an isothermal expansion, an isentropic expansion and an isothermal compression, concluding with an isentropic compression.

Carnot Cycle for a Heat Pump

The Carnot cycle is a theoretical thermodynamic cycle conducted on an ideal gas consisting of an isothermal expansion, an isentropic expansion and an isothermal compression, concluding with an isentropic compression.

Carnot Cycle for a Heat Engine

The Carnot cycle is a theoretical thermodynamic cycle conducted on an ideal gas consisting of an isothermal expansion, an isentropic expansion and an isothermal compression, concluding with an isentropic compression.

Cartesian-to-Polar-Coordinates Equations

The polar coordinate system is a two-dimensional coordinate system in which each point on a plane is determined by a distance from a reference point and an angle from a reference direction. These can be directly trans...

Casimir Effect

The Casimir effect describes the attractive force between two uncharged, perfectly conducting plates arising from quantum fluctuation effects.

Catheter Flow Rate

The catheter flow rate refers to the liquid volume flow from a catheter.

Centripetal Force Using Rotation Speed

A centripetal force is a force that makes a body follow a curved path. Its direction is always orthogonal to the motion of the body and toward the fixed point of the instantaneous center of curvature of the path.

Centripetal Force Using Angular Velocity

A centripetal force is a force that makes a body follow a curved path. Its direction is always orthogonal to the motion of the body and toward the fixed point of the instantaneous center of curvature of the path.

Centripetal Acceleration Using Rotation Speed

Centripetal acceleration is the rate of change of velocity of an object with respect to time as it moves in a circular path.

Centripetal Acceleration Using Angular Velocity

Centripetal acceleration is the rate of change of velocity of an object with respect to time as it moves in a circular path.

Centrifugal Pump Power

Centrifugal pump power describes the power of a certain class of pumps used to transport fluids by the conversion of rotational kinetic energy to the hydrodynamic energy of the fluid flow.

Chandrasekhar Number

The Chandrasekhar number is a dimensionless quantity used in magnetic convection to represent the ratio of the Lorentz force to the viscosity.

Charles's Law

Charles's law states that when the pressure on a sample of a dry gas is held constant, the Kelvin temperature and the volume will be directly related.

Cherenkov radiation is electromagnetic radiation emitted when a charged particle (such as an electron) passes through a dielectric medium at a speed greater than the phase velocity of light in that medium.

Circle Sector Area

The area of a sector of a circle depends on the size of that circle and the size of the arc for that sector.

Circle Chord Length by Apothem and Sagitta

A circle chord is a line segment whose endpoints lie on the circle. The sagitta is the distance from the center of the arc bridged by the chord to the center of the chord. The apothem is the distance from the center o...

Circle Chord Length by Angle and Radius

A circle chord is a line segment whose endpoints lie on the circle.

Circle Area

The area of a circle is π times the radius squared.

Circular Orbit Velocity

The circular orbit velocity describes the speed of an object in a stable orbit at a fixed distance around another body.

Circular Orbit Radius of a Charged Particle in a Magnetic Field

A charged particle moving in a magnetic field will be pushed into a circular path by the interaction of the charge and the magnetic field. The radius of that path can be calculated from the properties of the charge an...

Circular Current Loop

A circular current loop is a current constrained along a circular path by an infinitely thin wire.

Cloud Base Height

The cloud base is the lowest altitude of the visible portion of the cloud.

Cohen's d

Cohen's d is defined as the difference between two means divided by a standard deviation for the data.

Colebrook–White Equation for Pipe Roughness

The Colebrook–White equation expresses the Darcy friction factor as a function of the Reynolds number and pipe relative roughness, fitting the data of experimental studies of turbulent flow in smooth and rough pipes.

Colebrook–White Equation for Darcy–Weisbach Friction Factor

The Colebrook–White equation expresses the Darcy friction factor as a function of the Reynolds number and pipe relative roughness, fitting the data of experimental studies of turbulent flow in smooth and rough pipes.

Commodity Contracts Optimal Number

Calculate the optimal number of contracts to hedge a portfolio

Complement Probability

In probability theory, the complement of any event A is the event [not A], i.e. the event that A does not occur.

Compound Annual Growth Rate

Compound annual growth rate is a business- and investing-specific term for the geometric progression ratio that provides a constant rate of return over the time period.

Compton Shift

Compton scattering is the inelastic scattering of a photon by a charged particle, usually an electron. It results in a decrease in energy (increase in wavelength) of the photon, called the Compton effect. Part of the ...

Concave Mirror-Image Equations

A curved mirror is a mirror with a curved reflecting surface. A concave mirror bulges inward.

Concentration to Parts per Million in Water

Molar concentration is a measure of the concentration of a solute in a solution, or of any chemical species, in terms of the amount of substance in a given volume.

Concentration of Oxygen in Blood

Oxygen saturation is a relative measure of the concentration of oxygen that is dissolved or carried in a given medium as a proportion of the maximal concentration that can be dissolved in that medium.

Constant Translational Acceleration in a Straight Line

Constant translational acceleration in a straight line describes the equation of motion of an object moving under constant acceleration along a straight line as a function of time.

Constructive Thin-Film Interference

Thin-film interference is a natural phenomenon in which light waves reflected by the upper and lower boundaries of a thin film interfere with one another, either enhancing or reducing the reflected light. When the thi...

Continuous Capital Recovery Factor

A continuous capital recovery factor is the ratio of a constant annuity to the present value of receiving that annuity for a given length of time compounded continuously.

Convex Mirror-Image Equations

A curved mirror is a mirror with a curved reflecting surface. A convex mirror bulges outward.

Coriolis Effect

The Coriolis force is an inertial force that acts on objects that are in motion relative to a rotating reference frame. In a reference frame with clockwise rotation, the force acts to the left of the motion of the obj...

Corrective Lens Equation for Nearsightedness

The corrective lens equation for nearsightedness relates the far distance for a person to the necessary lens power to correct it.

Corrective Lens Equation for Farsightedness

The corrective lens equation for farsightedness relates the comfortable reading distance for a person to the necessary lens power to correct it.

Corrected QT Interval Using RR Interval

The QT interval is a measure of the time between the start of the Q wave and the end of the T wave in the heart's electrical cycle. It can be corrected for heart rate for improved detection of patients at increased ri...

Corrected QT Interval Using Heart Rate

The QT interval is a measure of the time between the start of the Q wave and the end of the T wave in the heart's electrical cycle. It can be corrected for heart rate for improved detection of patients at increased ri...

Coulomb's Law

The magnitude of the electrostatic force of attraction between two point charges is directly proportional to the product of the magnitudes of charges and inversely proportional to the square of the distance between th...

Cross-Country Skiing by Speed

The distance covered cross-country skiing equals the skier's speed times time.

Cross-Country Skiing by Pace

The time spent cross-country skiing equals the skier's pace times distance.

Cuboid Volume

The volume of a cuboid is the quantity of three-dimensional space enclosed by it.

Cylinder Volume

A cylinder is the surface formed by the points at a fixed distance from a given straight line called the axis of the cylinder. The volume is the space enclosed by the cylinder.

Cylinder Total Surface Area

A cylinder is the surface formed by the points at a fixed distance from a given straight line called the axis of the cylinder. Surface area refers to the area covered by all sides of the cylinder.

Cylinder Lateral Surface Area

A cylinder is the surface formed by the points at a fixed distance from a given straight line called the axis of the cylinder. Lateral surface area refers to the area covered by the curved side of the cylinder.

D

Damped Spring Harmonic Oscillator

A spring harmonic oscillator is a spring that, when displaced from its equilibrium position, experiences a restoring force proportional to the displacement. A damped spring harmonic oscillator experiences a frictional...

Damped Pendulum Harmonic Oscillator

A pendulum harmonic oscillator is a system that, when displaced from its equilibrium position, experiences a restoring force proportional to the displacement. A damped pendulum harmonic oscillator experiences a fricti...

Damped Driven Torsion Harmonic Oscillator

A torsion harmonic oscillator is a twisting system that, when displaced from its equilibrium position, experiences a restoring force proportional to the displacement. A damped driven torsion harmonic oscillator experi...

Damped Driven Spring Harmonic Oscillator

A spring harmonic oscillator is a spring that, when displaced from its equilibrium position, experiences a restoring force proportional to the displacement. A damped driven spring harmonic oscillator experiences a fri...

Damped Driven Pendulum Harmonic Oscillator

A pendulum harmonic oscillator is a system that, when displaced from its equilibrium position, experiences a restoring force proportional to the displacement. A damped driven pendulum harmonic oscillator experiences a...

Damped Driven Harmonic Oscillator

A harmonic oscillator is a system that, when displaced from its equilibrium position, experiences a restoring force, proportional to the displacement. A damped driven harmonic oscillator experiences a frictional force...

Dean Number

The Dean number is a dimensionless group in fluid mechanics, which occurs in the study of flow in curved pipes and channels.

Depth of Field for Photographic Lens

Depth of field is the distance between the nearest and farthest objects in a scene that appear acceptably sharp in an image.

Diesel Cycle

The Diesel cycle is a combustion process of a reciprocating internal combustion engine. In it, fuel is ignited by heat generated during the compression of air in the combustion chamber, into which fuel is then injected.

Differential Gear Ratio

The gear ratio is the relationship between the engine angular frequency and the angular frequency of the vehicle's wheels.

Differential Amplifier

A differential amplifier is a type of electronic amplifier that amplifies the difference between two input voltages, but suppresses any voltage common to the two inputs.

Dividend Discount Model

The dividend discount model is a method of valuing a company's stock price based on the theory that its stock is worth the sum of all of its future dividend payments, discounted back to their present values.

Dolbear's Law

Dolbear's law states the relationship between the air temperature and the rate at which crickets chirp. As temperatures rise, so does the frequency of chirps.

Doppler Shift Frequency Reduction Factor

The Doppler effect (or the Doppler shift) is the change in frequency or wavelength of a wave (or other periodic event) for an observer moving relative to its source.

Doppler Redshift

Doppler redshift is caused by movement of a source away from the observer. The term applies to any increase in wavelength and decrease in frequency caused by relative motion, even outside the visible spectrum.

Doppler Blueshift

Doppler blueshift is caused by movement of a source toward the observer. The term applies to any decrease in wavelength and increase in frequency caused by relative motion, even outside the visible spectrum.

Doyle's Log Rule

Doyle's log rule describes the volume of wood in a standing tree or log.

Drag Coefficient

The drag coefficient is a dimensionless quantity that is used to quantify the drag or resistance of an object in a fluid environment, such as air or water.

Drake Equation

The Drake equation is a probabilistic argument used to arrive at an estimate of the number of active, communicative extraterrestrial civilizations in the Milky Way galaxy.

Driven Torsion Harmonic Oscillator

A torsion harmonic oscillator is a twisting system that, when displaced from its equilibrium position, experiences a restoring force proportional to the displacement. A driven torsion harmonic oscillator experiences a...

Driven Spring Harmonic Oscillator

A spring harmonic oscillator is a spring that, when displaced from its equilibrium position, experiences a restoring force proportional to the displacement. A driven spring harmonic oscillator experiences an external ...

Damped Torsion Harmonic Oscillator

A torsion harmonic oscillator is a twisting system that, when displaced from its equilibrium position, experiences a restoring force proportional to the displacement. A damped torsion harmonic oscillator experiences a...

Damped Harmonic Oscillator

A harmonic oscillator is a system that, when displaced from its equilibrium position, experiences a restoring force proportional to the displacement. A damped harmonic oscillator experiences a frictional force (dampin...

Darcy's Law Using Pressure Difference

Darcy's law is an equation that describes the flow of a fluid through a porous medium.

Darcy's law is an equation that describes the flow of a fluid through a porous medium.

Data Transfer Speed

The data transfer rate is the amount of data that is conveyed per unit of time.

Deborah Number

The Deborah number is a dimensionless number often used in rheology that characterizes the fluidity of materials under specific flow conditions. It is based on the premise that given enough time, even a solid-like mat...

De Broglie Wavelength by Velocity

The de Broglie wavelength is the wavelength associated with a massive particle in motion according to quantum mechanics.

De Broglie Wavelength by Momentum

The de Broglie wavelength is the wavelength associated with a massive particle in motion according to quantum mechanics.

De Broglie Wavelength by Kinetic Energy

The de Broglie wavelength is the wavelength associated with a massive particle in motion according to quantum mechanics.

De Broglie Frequency by Velocity

The de Broglie frequency is the frequency associated with a massive particle in motion according to quantum mechanics.

De Broglie Frequency by Kinetic Energy

The de Broglie frequency is the frequency associated with a massive particle in motion according to quantum mechanics.

De Broglie Angular Frequency by Velocity

The de Broglie angular frequency is the angular frequency associated with a massive particle in motion according to quantum mechanics.

De Broglie Angular Frequency by Momentum

The de Broglie angular frequency is the angular frequency associated with a massive particle in motion according to quantum mechanics.

Decibel-to-Ratio Conversion

The decibel is a logarithmic unit used to express the ratio of two values of a physical quantity.

De Laval Nozzle

A de Laval nozzle is a tube that is pinched in the middle, making a carefully balanced, asymmetric hourglass shape. It is used to accelerate a hot, pressurized gas passing through it to a higher supersonic speed in th...

Destructive Thin-Film Interference

Thin-film interference is a natural phenomenon in which light waves reflected by the upper and lower boundaries of a thin film interfere with one another, either enhancing or reducing the reflected light. When the thi...

Differential Bending of a Bimetallic Strip

A bimetallic strip is used to convert a temperature change into mechanical displacement. The differential bending of a bimetallic strip describes the radius of curvature as a function of temperature and the length and...

Diffraction Intensity Ratio for Circular Aperture Diffraction

The diffraction intensity ratio is the ratio between intensity at a given angle and the incident intensity of light passing through a circular aperture.

Diffraction Grating with Incidence Angle

A diffraction grating is an optical component with a periodic structure, which splits and diffracts light into several beams traveling in different directions. The directions of these beams depend on the spacing of th...

Diffraction Grating

A diffraction grating is an optical component with a periodic structure, which splits and diffracts light into several beams traveling in different directions. The directions of these beams depend on the spacing of th...

Dilution is a reduction in the pH of a chemical (gas, vapor, solution). It is the process of decreasing the concentration of a solute in solution, usually simply by mixing with more solvent. To dilute a solution means...

Dilution Equation

Dilution is a reduction in the pH of a chemical (gas, vapor, solution). It is the process of decreasing the concentration of a solute in solution, usually simply by mixing with more solvent. To dilute a solution means...

Discounted Security

A security is a tradable financial asset. A discounted security's rate is based on the redemption value rather than the price.

Dittus–Boelter Equation

The Dittus–Boelter equation (for turbulent flow) is an explicit function for calculating the Nusselt number. The Nusselt number is the ratio of convective to conductive heat transfer across (normal to) the boundary.

Doppler-Shifted Frequency

The Doppler effect (or the Doppler shift) is the change in frequency or wavelength of a wave (or other periodic event) for an observer moving relative to its source.

Drag Force on a Sphere for Stokes Flow

Stokes flow is a type of fluid flow where advective inertial forces are small compared with viscous forces.

Driven Pendulum Harmonic Oscillator

A pendulum harmonic oscillator is a system that, when displaced from its equilibrium position, experiences a restoring force proportional to the displacement. A driven pendulum harmonic oscillator experiences an exter...

Duration-Based Hedge Ratio

Calculation of the optimal futures contracts

E

Earth Satellite Period in a Circular Orbit

A circular orbit is the orbit at a fixed distance around any point by an object rotating around a fixed axis. The orbital period is the time it takes the object to revolve around the point, in this case the planet Earth.

Earthquake Rupture Length

The rupture length is the length of an earthquake rupture, which is a slip, whether on the surface or beneath, in the Earth's crust that results in a fault and displacement of some sort.

Earthquake Rupture Area

The rupture area is the area of an earthquake rupture, which is a slip, whether on the surface or beneath, in the Earth's crust that results in a fault and displacement of some sort.

Earthquake Fault Slip Rate

Slip is defined as the relative movement of geological features present on either side of a fault plane, and is a displacement vector. A fault's sense of slip is defined as the relative motion of the rock on each side...

Earthquake Fault Slip

Slip is defined as the relative movement of geological features present on either side of a fault plane, and is a displacement vector. A fault's sense of slip is defined as the relative motion of the rock on each side...

Earthquake Downdip Rupture Width

The downdip rupture width is the average width of a rupture surface measured in the downdip direction.

Eckert Number

The Eckert number is a dimensionless number used in continuum mechanics. It expresses the relationship between a flow's kinetic energy and the boundary layer enthalpy difference, and is used to characterize heat dissi...

Economic value added is an estimate of a firm's economic profit, or the value created in excess of the required return of the company's shareholders. Economic value added is the net profit less the equity cost of the ...

Ekman Number

The Ekman number is a dimensionless number used in fluid dynamics to describe the ratio of viscous forces to Coriolis forces.

Elastic Collision

An elastic collision is an encounter between two bodies in which the total kinetic energy of the two bodies after the encounter is equal to their total kinetic energy before the encounter. Perfectly elastic collisions...

Equations of Motion for a Round Object on an Inclined Plane Using Slope

The equations of motion for a round object on an inclined plane are the equations that describe the behavior of the object in terms of its motion as a function of time. An inclined plane is a flat supporting surface t...

Equations of Motion for a Round Object on an Inclined Plane

The equations of motion for a round object on an inclined plane are the equations that describe the behavior of the object in terms of its motion as a function of time. An inclined plane is a flat supporting surface t...

Equation of Circular Motion under Constant Acceleration

The equation of circular motion describes an object moving under constant angular acceleration in a circular as a function of time.

Eccentricity of an Ellipse

An ellipse is a curve in a plane surrounding two focal points such that the sum of the distances to the two focal points is constant for every point on the curve. The shape of an ellipse (how \"elongated\" it is) is r...

Elastic Surface Collision

An elastic surface collision is an encounter between a particle and a surface in which the kinetic energy of the particle after the encounter is equal to the kinetic energy before the encounter. Perfectly elastic coll...

Elastic Collision in Two Dimensions Using Incident Angle

An elastic collision is an encounter between two bodies in which the total kinetic energy of the two bodies after the encounter is equal to their total kinetic energy before the encounter. Perfectly elastic collisions...

Elastic Collision in Two Dimensions Using Impact Parameter

An elastic collision is an encounter between two bodies in which the total kinetic energy of the two bodies after the encounter is equal to their total kinetic energy before the encounter. Perfectly elastic collisions...

Electromagnetic Skin Depth

Skin depth is a property of the skin effect, the tendency of an alternating electric current (AC) to become distributed within a conductor such that the current density is largest near the surface of the conductor, an...

Electric Resistivity Formula

The electrical resistivity is an intrinsic property that quantifies how strongly a given material opposes the flow of electric current.

Electric Power Using Voltage and Current

Electric power is the rate, per unit time, at which electrical energy is transferred by an electric circuit.

Electric Power Using Resistance and Voltage

Electric power is the rate, per unit time, at which electrical energy is transferred by an electric circuit.

Electric Power Using Resistance and Current

Electric power is the rate, per unit time, at which electrical energy is transferred by an electric circuit.

Electric Field of Solid Charged Sphere

The electric field of a solid charged sphere describes a vector field that associates to each point in space the Coulomb force that would be experienced per unit of electric charge, by an infinitesimal test charge at ...

Electric Field of Hollow Charged Sphere

The electric field of a hollow charged sphere describes a vector field that associates to each point in space the Coulomb force that would be experienced per unit of electric charge, by an infinitesimal test charge at...

Electric Field of a Point Charge

A point charge is an idealized model of a particle that has an electric charge. A point charge is an electric charge at a mathematical point with no dimensions.

Electrical Energy

Electrical energy is the energy newly derived from electric potential energy or kinetic energy.

Elliptical Machine Using Speed

An elliptical machine is a stationary exercise machine used to simulate stair climbing, walking or running without causing excessive pressure to the joints, hence decreasing the risk of impact injuries.

Elliptical Machine Using Pace

An elliptical machine is a stationary exercise machine used to simulate stair climbing, walking or running without causing excessive pressure to the joints, hence decreasing the risk of impact injuries.

An elliptical machine is a stationary exercise machine used to simulate stair climbing, walking or running without causing excessive pressure to the joints, hence decreasing the risk of impact injuries.

Elliptical Cylinder Volume

An elliptical cylinder is a cylinder whose cross-section is an ellipse.

Elliptical Cylinder Mass

An elliptical cylinder is a cylinder whose cross-section is an ellipse.

Ellipsoid Volume

An ellipsoid is a surface that may be obtained from a sphere by deforming it by means of directional scalings, or more generally, of an affine transformation.

Ellipse Area

Ellipse area calculates the area of an ellipse.

Energy Formula for Luminosity

Luminosity is the total amount of energy emitted by a star, galaxy or other astronomical object per unit time.

Energy Efficiency

Energy conversion efficiency is the ratio between the useful output of an energy conversion machine and the input, in energy terms.

Energy Density of Magnetic Field

A magnetic field is the magnetic effect of electric currents and magnetic materials. Energy is needed to generate a magnetic field both to work against the electric field that a changing magnetic field creates and cha...

Engineering Strain

Strain is a measure of deformation representing the displacement between particles in the body relative to a reference length.

Equation of Motion Using Final and Initial Position

Equations of motion are equations that describe the behavior of a physical system in terms of its motion as a function of time.

Equation of Motion Using Final and Initial Angle

Equations of motion are equations that describe the behavior of a physical system in terms of its motion as a function of time.

Equation of Motion Using Distance

Equations of motion are equations that describe the behavior of a physical system in terms of its motion as a function of time.

Equation of Motion Using Angular Displacement

Equations of motion are equations that describe the behavior of a physical system in terms of its motion as a function of time.

Equivalent Sound Level for Fixed Sources

Sound intensity level is the level of the intensity of a sound relative to a reference value.

The equivalent dose is a dose quantity representing the stochastic health effects of low levels of ionizing radiation on the human body. Ionizing radiation is radiation that carries enough energy to free electrons fro...

Ericsson Cycle

The Ericsson cycle consists of an isothermal compression, an isobaric heat addition, an isothermal expansion and an isobaric heat removal.

Erlang C Formula

The Erlang C formula determines the probability of packet loss or delay if blocked calls are queued until served.

Erlang B Formula

The Erlang B formula determines the probability of packet loss or delay if blocked calls are aborted.

Escape Velocity

The escape velocity is the minimum speed needed for an object to escape from the gravitational influence of a massive body.

Eötvös Number

The Eötvös number, also called the Bond number, is a dimensionless number measuring the importance of gravitational forces compared to surface tension forces, and is used (together with the Morton number) to character...

Buckling is a mathematical instability that leads to a failure mode. The critical load is the point when the load on a column forces a bifurcation of the states of equilibrium: a purely compressed state (with no later...

Euler Characteristic

The Euler characteristic is a topological invariant, a number that describes a topological space's shape or structure regardless of the way it is bent.

Expanded Boiling-Point Elevation Equation

Boiling-point elevation describes the phenomenon in which the boiling point of a liquid (a solvent) will be higher when another compound is added, meaning that a solution has a higher boiling point than a pure solvent...

Expected Fielding Independent Pitching

Expected fielding independent pitching is a measurement of a pitcher's performance that controls for the quality of his team's defense.

Exponential Decay

Exponential decay is the decrease in the amount of a substance at a rate proportional to its current value.

Exposure Value

Exposure value is a number that represents a combination of a camera's shutter speed and f-number, such that all combinations that yield the same exposure have the same exposure value (for any fixed scene luminance).

F

Fabry–Pérot Interferometer Using Plate Reflectance

This formula describes the transmission and reflection of light through a Fabry­Pérot interferometer, or etalon, a transparent plate with two reflecting surfaces or two parallel, highly reflecting mirrors.

Fabry–Pérot Interferometer Using Finesse Coefficient

This formula describes the transmission and reflection of light through a Fabry­Pérot interferometer, or etalon, a transparent plate with two reflecting surfaces or two parallel, highly reflecting mirrors.

Fanno Flow

Fanno flow describes the adiabatic flow through a constant area duct where the effect of friction is considered.

Fermi–Dirac Distribution for Non-interacting Fermions

The Fermi–Dirac distribution describes how particles are distributed over energy states in systems consisting of many identical particles that obey the Pauli exclusion principle.

Fermi Energy for Non-Interacting Fermions

The Fermi energy is a concept in quantum mechanics usually referring to the energy difference between the highest and lowest occupied single-particle states in a quantum system of non-interacting fermions at absolute ...

Fielding Independent Pitching

Fielding independent pitching is a measurement of a pitcher's performance that controls for the quality of his team's defense.

Field of View

The field of view is the portion of the focused subject visible through the camera lens, assuming a rectilinear lens.

First Euler Number Using Pressure Difference

The Euler number is a dimensionless number used in fluid flow calculations. It expresses the relationship between a local pressure drop caused by a restriction and the kinetic energy per volume of the flow, and is use...

First Euler Number Using Friction Force

The Euler number is a dimensionless number used in fluid flow calculations. It expresses the relationship between a local pressure drop caused by a restriction and the kinetic energy per volume of the flow, and is use...

First Cowling Number

The Cowling number expresses the magnetic-to-inertia forces ratio.

First Law of Thermodynamics

The first law of thermodynamics states that the change in the internal energy of a closed system is equal to the amount of heat supplied to the system minus the amount of work done by the system on its surroundings.

First Knudsen Number

The Knudsen number is a dimensionless number defined as the ratio of the molecular mean free path length to a representative physical length scale.

First-Order Arrhenius Equation

The Arrhenius equation is a formula for the temperature dependence of reaction rates.

Flow Rate for Rectangular Pipes

The volumetric flow rate is the volume of fluid that passes per unit time.

Flow Rate for Circular Pipes

The volumetric flow rate is the volume of fluid that passes per unit time.

f-Number Arithmetic

The f-number of an optical system, such as a camera lens, is the ratio of the system's focal length to the diameter of the entrance pupil. It is a quantitative measure of lens speed.

f-Number

The f-number of an optical system, such as a camera lens, is the ratio of the system's focal length to the diameter of the entrance pupil. It is a quantitative measure of lens speed.

Football Passer Rating

The Passer rating is a measure of the performance of passers, primarily quarterbacks, in American football and Canadian football.

Force Components

The force components describe how the force is distrubuted along the x and y axes of a surface.

Fourier's Law

The law of heat conduction, also known as Fourier's law, states that the time rate of heat transfer through a material is proportional to the negative gradient in the temperature and to the area, at right angles to th...

Fourier Number Using Thermal Diffusivity

The Fourier number is a dimensionless number that characterizes transient heat conduction. Conceptually, it is the ratio of diffusive or conductive transport rate to the quantity storage rate, where the quantity may b...

Fourier Number Using Thermal Conductivity

The Fourier number is a dimensionless number that characterizes transient heat conduction. Conceptually, it is the ratio of diffusive or conductive transport rate to the quantity storage rate, where the quantity may b...

Fourier Number for Mass Transfer

The Fourier number is a dimensionless number that characterizes transient heat conduction. Conceptually, it is the ratio of diffusive or conductive transport rate to the quantity storage rate, where the quantity may b...

Free Water Deficit

Body water is the water content of an animal body that is contained in the tissues, the blood, the bones and elsewhere. The percentages of body water contained in various fluid compartments add up to total body water.

Freezing-Point Depression Equation Using Solvent Properties

Freezing-point depression is the process in which adding a solute to a solvent decreases the freezing point of the solvent.

Freezing-Point Depression Equation Using Cryoscopic Constant

Freezing-point depression is the process in which adding a solute to a solvent decreases the freezing point of the solvent.

Frequency Period Relation

Frequency is the number of occurrences of a repeating event per unit time. The period is the duration of time of one cycle in a repeating event, so the period is the reciprocal of the frequency.

Fresnel Number

The Fresnel number is the difference, expressed in half-wavelengths, between the slant distance from the observation point to the edge of the aperture and the orthogonal distance from the observation point to the cent...

Fresnel Equations for S-Polarized Light

The Fresnel equations calculate the reflection and transmission coefficients for light incident on an interface between media of differing refractive indices.

Fresnel Equations for P-Polarized Light

The Fresnel equations calculate the reflection and transmission coefficients for light incident on an interface between media of differing refractive indices.

Froude Number

The Froude number is a dimensionless number defined as the ratio of the flow inertia to the external field (the latter in many applications simply due to gravity).

Fuel Cost

The fuel economy of an automobile is the fuel-efficiency relationship between the distance traveled and the amount of fuel consumed by the vehicle.

Fuel Used

The fuel economy of an automobile is the fuel efficiency relationship between the distance traveled and the volume of fuel consumed by the vehicle.

Future Value of Annuity Due

An annuity is a series of payments made at equal intervals. An annuity due is an annuity whose payments are made at the beginning of each period. The future value of an annuity due is the accumulated amount, including...

Future Value of Annuity

An annuity is a series of payments made at equal intervals. The future value of an annuity is the accumulated amount, including payments and interest, of a stream of payments made to an interest-bearing account.

G

Gravitational Acceleration

Gravitational acceleration is the acceleration on an object caused by the force of gravitation.

Galileo Number Using Reynolds Number

The Galileo number is proportional to gravity forces divided by viscous forces. The Galileo number is used in viscous flow and thermal expansion calculations—for example, to describe fluid film flow over walls. These ...

Galileo Number Using Characteristic Length

The Galileo number is proportional to gravity forces divided by viscous forces. The Galileo number is used in viscous flow and thermal expansion calculations—for example, to describe fluid film flow over walls. These ...

Gambling Winnings Using Fractional Odds

Fractional odds quote the net total that will be paid out to the bettor, should he or she win, relative to the bet.

Gambling Winnings Using Decimal Odds

Decimal odds quote the ratio of the payout amount, including the original bet, to the bet itself.

Gambling Winnings Using American Odds

The American odds indicate how much money will be won on a \$100 wager.

Gas Particles' Velocity

The thermal velocity or thermal speed is a typical velocity of the thermal motion of particles that make up a gas.

Gay–Lussac's Law

The pressure of a gas of fixed mass and fixed volume is directly proportional to the gas's absolute temperature.

Gay–Lussac Number

The Gay­Lussac number characterizes the relative thermal volume expansion of substances.

Glass's δ

Glass's δ is an estimator of the population effect size that uses only the standard deviation of the second group. An effect size is a quantitative measure of the strength of a phenomenon. A population effect size bas...

Goff–Gratch Equation for Water

The Goff–Gratch equation is an experimental correlation proposed to estimate the saturation water vapor pressure at a given temperature.

Goff–Gratch Equation for Ice

The Goff–Gratch equation is an experimental correlation proposed to estimate the saturation water vapor pressure at a given temperature.

Golden Ratio

Two quantities are in the golden ratio if their ratio is the same as the ratio of their sum to the larger of the two quantities.

Graetz Number

The Graetz number is a dimensionless number that characterizes laminar flow in a conduit.

Graham's Law of Diffusion

Graham's law of effusion (sometimes called Graham's law of diffusion) states that the rate of effusion of a gas is inversely proportional to the square root of the mass of its particles.

Grashof Number

The Grashof number is a dimensionless number in fluid dynamics and heat transfer that approximates the ratio of the buoyancy to viscous force acting on a fluid.

Gravitational Time Dilation Using Mass

Gravitational time dilation is a form of time dilation, an actual difference of elapsed time between two events as measured by observers situated at varying distances from a gravitating mass. The higher the gravitatio...

Gravitational Time Dilation Using Gravity

Gravitational time dilation is a form of time dilation, an actual difference of elapsed time between two events as measured by observers situated at varying distances from a gravitating mass. The higher the gravitatio...

Gravitational Redshift

Gravitational redshift is the process by which electromagnetic radiation originating from a source that is in a gravitational field is reduced in frequency, or redshifted, when observed in a region at a higher gravita...

Gravitational Potential Energy

Gravitational potential energy is the energy of an object due to gravity near the surface of a gravitating body.

Gravitational Binding Energy of a Uniform Sphere

The gravitational binding energy is the minimum energy that must be added to a system for the system to cease being in a gravitationally bound state.

Gravitational Acceleration for a Uniform Density Sphere

Gravitational acceleration for a uniform density sphere is the acceleration on an object caused by the force of gravitation.

Gross Domestic Product Production

The production approach to gross domestic product looks at the value added to goods sold.

Gross Domestic Product Income

Gross domestic product using the income approach looks at the sum of primary incomes distributed by resident producer units.

Gross Domestic Product Expenditures

Gross domestic product using the expenditure approach uses the sum of the final uses of goods and services measured in purchasers' prices.

Gyromagnetic Ratio

The gyromagnetic ratio (also sometimes known as the magnetogyric ratio in other disciplines) of a particle or system is the ratio of its magnetic moment to its angular momentum.

H

Hartmann Number

The Hartmann number, related to the Chandrasekhar number, is a dimensionless quantity used in magnetic convection to represent the ratio of the Lorentz force to the viscosity.

Hazen–Williams Equation

The Hazen–Williams equation is an empirical relationship that relates the flow of water in a pipe with the physical properties of the pipe and the pressure drop caused by friction.

Heat Capacity Ratio Using Specific Heat Capacities

The heat capacity ratio is the ratio of the heat capacity at constant pressure to heat capacity at constant volume.

Heat Capacity Ratio Using Heat Capacities

The heat capacity ratio is the ratio of the heat capacity at constant pressure to heat capacity at constant volume.

Heat Capacity Ratio Using Degrees of Freedom

The heat capacity ratio is the ratio of the heat capacity at constant pressure to heat capacity at constant volume.

Heat Capacity of an Ideal Gas by Number of Particles

Heat capacity, or thermal capacity, of an ideal gas is a measurable physical quantity equal to the ratio of the heat added (or removed) to the resulting temperature change. An ideal gas is a theoretical gas composed o...

Heat Capacity of an Ideal Gas by Amount

Heat capacity or thermal capacity of an ideal gas is a measurable physical quantity equal to the ratio of the heat added (or removed) to the resulting temperature change. An ideal gas is a theoretical gas composed of ...

Heat Engine Efficiency

A heat engine is a system that converts heat or thermal energy to mechanical energy, which can then be used to do mechanical work.

Heat Transfer Coefficient

The heat transfer coefficient is the proportionality constant between the heat flux and the thermodynamic driving force for the flow of heat.

Hedge Effectiveness

Hedge effectiveness is the extent to which a hedge transaction results in offsetting changes in fair value or cash flow that the transaction was intended to provide (as identified by the hedging entity).

Heisenberg Uncertainty Principle for Position and Momentum

The uncertainty principle, also known as Heisenberg's uncertainty principle or Heisenberg's indeterminacy principle, is any of a variety of mathematical inequalities asserting a fundamental limit to the precision with...

Heisenberg Uncertainty Principle for Energy and Time

The uncertainty principle, also known as Heisenberg's uncertainty principle or Heisenberg's indeterminacy principle, is any of a variety of mathematical inequalities asserting a fundamental limit to the precision with...

Helmholtz Resonator Frequency

Helmholtz resonance is the phenomenon of air resonance in a cavity, such as when one blows across the top of an empty bottle.

Helmholtz Coil Field at Center

A Helmholtz coil is a device for producing a region of nearly uniform magnetic field. It consists of two solenoid electromagnets on the same axis.

Helmholtz Coil Field at Arbitrary Distance

A Helmholtz coil is a device for producing a region of nearly uniform magnetic field. It consists of two solenoid electromagnets on the same axis.

Henderson–Hasselbalch Equation Using Log Acidity Constant

The Henderson–Hasselbalch equation describes the derivation of pH as a measure of acidity (using pKa, the negative log of the acid dissociation constant) in biological and chemical systems.

Henderson–Hasselbalch Equation Using Acidity Constant

The Henderson–Hasselbalch equation describes the derivation of pH as a measure of acidity (using pKa, the negative log of the acid dissociation constant) in biological and chemical systems.

Heron's Formula

Heron's formula (sometimes called Hero's formula) gives the area of a triangle by requiring no arbitrary choice of side as base or vertex as origin.

Hohmann Transfer Time Using Semimajor Axis

The Hohmann transfer orbit is an elliptical orbit used to transfer between two circular orbits of different radii in the same plane. The transfer time is the time it takes to complete the transit along the orbit.

The Hohmann transfer orbit is an elliptical orbit used to transfer between two circular orbits of different radii in the same plane. The transfer time is the time it takes to complete the transit along the orbit.

Hohmann Total Delta-V

The Hohmann transfer orbit is an elliptical orbit used to transfer between two circular orbits of different radii in the same plane. The total delta-v is the change in velocity needed to enter and exit the elliptical ...

Hohmann Exit Delta-V

The Hohmann transfer orbit is an elliptical orbit used to transfer between two circular orbits of different radii in the same plane. The exit delta-v is the change in velocity needed to exit the elliptical orbit.

Hohmann Entrance Delta-V

The Hohmann transfer orbit is an elliptical orbit used to transfer between two circular orbits of different radii in the same plane. The entrance delta-v is the change in velocity needed to enter the elliptical orbit.

Hohmann Angular Alignment

The Hohmann transfer orbit is an elliptical orbit used to transfer between two circular orbits of different radii in the same plane. The angular alignment is the bearing needed to make the transfer.

Hooke's Law for Potential Energy

Hooke's law is a principle of physics that states that the force needed to extend or compress a spring by some distance is proportional to that distance.

Hooke's Law for Force

Hooke's law is a principle of physics that states that the force needed to extend or compress a spring by some distance is proportional to that distance.

Horizon Distance

The horizon or skyline is the apparent line that separates earth from sky, the line that divides all visible directions into two categories: those that intersect the Earth's surface, and those that do not.

Hydraulic Conductivity

Hydraulic conductivity is a property of vascular plants, soils and rocks that describes the ease with which a fluid (usually water) can move through pore spaces or fractures. It depends on the intrinsic permeability o...

Hydrostatic Pressure

Hydrostatic pressure describes the pressure in a fluid at rest, where all frictional and inertial stresses vanish.

Hyperfocal Distance

Hyperfocal distance is the nearest focused distance such that the point at infinity still appears sharp.

Hypsometric Equation

The hypsometric equation, also known as the thickness equation, relates an atmospheric pressure ratio to the equivalent thickness of an atmospheric layer under the assumptions of constant temperature and gravity.

I

Ideal Gas Law Using Volume

The ideal gas law is the equation of state of a hypothetical ideal gas. An ideal gas is a theoretical gas composed of many randomly moving point particles whose only interactions are perfectly elastic collisions.

Ideal Gas Law Using Density

The ideal gas law is the equation of state of a hypothetical ideal gas. An ideal gas is a theoretical gas composed of many randomly moving point particles whose only interactions are perfectly elastic collisions.

Ideal Transformer Voltage Equation

A transformer is an electrical device that transfers electrical energy between two or more circuits through electromagnetic induction. A varying current in one coil of the transformer produces a varying magnetic field...

Ideal Transformer Current Equation

A transformer is an electrical device that transfers electrical energy between two or more circuits through electromagnetic induction. A varying current in one coil of the transformer produces a varying magnetic field...

Ideal Rocket Equation

The ideal rocket equation describes the motion of vehicles that follow the basic principle of a rocket: a device that can apply acceleration to itself using thrust by expelling part of its mass with high velocity, and...

Illuminance from Luminous Intensity

Illuminance is the total luminous flux incident on a surface, per unit area.

Impulse for Constant Force

Impulse is the integral of a force, F, over the time interval, t, for which it acts.

Inclined Span Catenary Sag

The inclined span catenary sag describes the tensions and sagging curve, or catenary, of a cable connecting two points at different elevations.

Indicated Horsepower

Indicated horsepower is the theoretical power produced in a reciprocating engine if it is completely frictionless in converting the expanding gas energy in the cylinders.

Inductor-Stored Energy

Inductor-stored energy is the energy stored in an inductor, a passive two-terminal electrical component that stores electrical energy in a magnetic field when electric current is flowing through it.

Inductor Reactance Formula

The inductive reactance is the opposition of a circuit element to a change in current or voltage, due to that element's inductance.

Infinitely Long Wire Magnetic Field

A magnetic field is the magnetic effect of electric currents and magnetic materials for an infinitely long wire; it is created by the current flowing through the wire.

Instrumentation Amplifier

An instrumentation amplifier is a type of differential amplifier that has been outfitted with input buffer amplifiers, which eliminate the need for input impedance matching, and thus make the amplifier particularly su...

Insulin Dose Adjustment for the Day of Westward Travel

The adjusted insulin dose is the total doses of insulin that a traveler needs to take to account for time zones crossed.

Insulin Dose Adjustment for the Day of Eastward Travel

The adjusted insulin dose is the total doses of insulin that a traveler needs to take to account for time zones crossed.

Intensity Ratio for Apparent Magnitude

The apparent magnitude of a celestial object is a number that is a measure of its brightness as seen by an observer on Earth.

Interest at Maturity Security

Interest at maturity securities are interest-bearing securities that pay the face amount plus a coupon on the maturity date.

International 1/4-Inch Log Rule

The international 1/4-inch log rule determines the volume of lumber from a log, accounting for the taper that exists in all logs, saw kerf (or the loss of wood as sawdust) and wood removed on the outside of the logs f...

Internal Energy of an Ideal Gas Using Particle Number

The internal energy of a system is the energy contained within the system, excluding the kinetic energy of motion of the system as a whole and the potential energy of the system as a whole due to external force fields...

Internal Energy of an Ideal Gas Using Molar Amount

The internal energy of a system is the energy contained within the system, excluding the kinetic energy of motion of the system as a whole and the potential energy of the system as a whole due to external force fields...

Intrinsic Permeability

Permeability in fluid mechanics and the earth sciences is a measure of the ability of a porous material (often a rock or an unconsolidated material) to allow fluids to pass through it. Intrinsic permeability is permea...

Inverting Amplifier

An inverting amplifier is an operational amplifier where the output voltage changes in an opposite direction to the input voltage. An operational amplifier (often op-amp or opamp) is a DC-coupled, high-gain electronic...

Isobaric Process

An isobaric process is a thermodynamic process in which the pressure stays constant.

Isochoric Process

An isochoric process is a thermodynamic process during which the volume of the closed system undergoing such a process remains constant.

Isothermal Process

An isothermal process is a change of a system in which the temperature remains constant.

IV Infusion Rate

Intravenous therapy is the infusion of liquid substances directly into a vein. The infusion rate is the rate at which a solution is administered to the patient.

J

Jeans Mass Using Speed of Sound

The Jeans mass is the mass that a spherical cloud of interstellar gas must have in order to contract under its own weight.

Jeans Length Using Temperature

The Jeans length is the critical radius for the instability of a collapsing thermalized cloud of self­gravitating gas.

Jeans Length Using Speed of Sound

The Jeans length is the critical radius for instability of a collapsing thermalized cloud of self­gravitating gas.

Johnson–Nyquist Noise Voltage

The Johnson–Nyquist noise is the electronic noise generated by the thermal agitation of the charge carriers (usually the electrons) inside an electrical conductor at equilibrium, which happens regardless of any applie...

Johnson–Nyquist Noise Power Spectral Density

The Johnson–Nyquist noise is the electronic noise generated by the thermal agitation of the charge carriers (usually the electrons) inside an electrical conductor at equilibrium, which happens regardless of any applie...

Joule's Law Using Electric Potential

Joule's first law states that the power of heating generated by an electrical conductor is proportional to the product of its resistance and the square of the current.

K

Kepler's Third Law

Kepler's laws of planetary motion are three scientific laws describing the motion of planets around the Sun. The third law states that the square of the orbital period of a planet is proportional to the cube of the se...

Kepler's First Law

Kepler's laws of planetary motion are three scientific laws describing the motion of planets around the Sun. The first law states that the orbit of a planet is an ellipse with the Sun at one of the two foci.

Kinetic Friction Coefficient

Kinetic friction is the force resisting the relative motion of solid surfaces sliding against each other.

Kinetic Energy

The kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity.

Knoop Hardness

The Knoop hardness is the measure of the Knoop hardness test, a micro-hardness test for mechanical hardness used particularly for very brittle materials or thin sheets, where only a small indentation may be made for t...

L

Larmor Power

The Larmor formula is used to calculate the total power radiated by a nonrelativistic point charge as it accelerates or decelerates.

Larmor Frequency

The Larmor precession is the precession of the magnetic moment of an object about an external magnetic field. The Larmor frequency is the frequency of that procession.

Law of Cosines

The law of cosines relates the lengths of the sides of a triangle to the cosine of one of its angles.

Law of Haversines

The haversine formula determines the great-circle distance between two points on a sphere given their longitudes and latitudes.

Law of Tangents

The law of tangents is a statement about the relationship between the tangents of two angles of a triangle and the lengths of the opposing sides.

Law of Sines

The law of sines is an equation relating the lengths of the sides of a triangle (any shape) to the sines of its angles.

Lenoir Cycle

The Lenoir cycle is an idealized thermodynamic cycle often used to model a pulsejet engine.

Lensmaker's Equation

A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. The lensmaker's equation describes the relationship between focal length and the radii of curvature of the lens.

Level Span Catenary Sag

The level span catenary sag describes the tensions and sagging curve, or catenary, of a cable connecting two points at the same elevation.

Lewis Number Using Thermal Diffusivity

The Lewis number is a dimensionless number defined as the ratio of thermal diffusivity to mass diffusivity. It is used to characterize fluid flows where there is simultaneous heat and mass transfer.

Lewis Number Using Thermal Conductivity

The Lewis number is a dimensionless number defined as the ratio of thermal diffusivity to mass diffusivity. It is used to characterize fluid flows where there is simultaneous heat and mass transfer.

Lift Coefficient

The lift coefficient is a dimensionless coefficient that relates the lift generated by a lifting body to the fluid density around the body, the fluid velocity and an associated reference area.

Logistic Equation

The logistic equation is used to calculate population growth—the increase in the number of individuals in a population.

Log Odds Ratio

The log odds ratio is a way to quantify how strongly the presence or absence of property A is associated with the presence or absence of property B in a given population.

Lorentz Number

The Lorentz number is a dimensionless number that relates the thermal conductivity of a metal to its temperature and its electrical conductivity.

Lorentz Force Using Current

The Lorentz force is the combination of electric and magnetic force on a point charge due to electromagnetic fields.

Lorentz Factor

The Lorentz factor is the factor by which time, length and relativistic mass change for an object while that object is moving.

Luminosity Formula for Apparent Magnitude

Luminosity is the total amount of energy emitted by a star, galaxy or other astronomical object per unit time. The apparent magnitude of a celestial object is a number that is a measure of its brightness as seen by an...

Luminosity Formula for Absolute Magnitude

Luminosity is the total amount of energy emitted by a star, galaxy or other astronomical object per unit time. Absolute magnitude is a measure of the luminosity of a celestial object on a logarithmic astronomical magn...

M

Moment of Inertia of a Thin Disk

The mass moment of inertia measures the extent to which an object resists rotational acceleration about a particular axis, and is the rotational analog to mass. For a disk of infinitesimal thickness, the moments of in...

Moment of Inertia of a Cuboid

The mass moment of inertia measures the extent to which an object resists rotational acceleration about a particular axis, and is the rotational analog to mass. For a uniform solid cuboid, the moment of inertia is tak...

Macaulay Duration of Bonds

Modified duration is the name given to the weighted average time until cash flows are received, and is measured in years.

Mach Number

The Mach number is a dimensionless quantity representing the ratio of flow velocity past a boundary to the local speed of sound.

Magnetic Reynolds Number

The magnetic Reynolds number is the magnetic analog of the Reynolds number, a fundamental dimensionless group that occurs in magnetohydrodynamics. It gives an estimate of the relative effects of advection or induction...

Magnetic Field in an Infinitely Long Solenoid

A solenoid is a coil wound into a tightly packed helix.

Manning Formula

The Manning formula is an empirical formula estimating the average velocity of a liquid flowing in a conduit that does not completely enclose the liquid, such as open-channel flow.

Mass Density

The mass density of a substance is its mass per unit volume.

Mass-Luminosity Relation for Main Sequence Stars

Luminosity is the total amount of energy emitted by a star, galaxy or other astronomical object per unit time. For stars on the main sequence, luminosity is related to mass.

Material Moduli Relationship

The material moduli relationship describes the relationship between the Young's modulus and the torsion modulus.

Maximal Magnetic Induction in a Circular Coil

Magnetic induction is the production of an electromotive force across an electrical conductor due to its dynamic interaction with a magnetic field.

Maximum Stable Sand Castle Height

A sand castle is a type of sand sculpture resembling a miniature building. Its height depends on a number of factors, such as the shape, size and mixture of the sand grains, the moisture content and the details of the...

Maximum Spring Force

The maximum spring force is the maximum force the spring can exert before permanent deformation.

Maximum Shear Stress in Spring

The maximum shear stress in a spring is the maximum shear stress the spring can suffer before permanent deformation.

Mean Free Path Using Pressure

The mean free path is the average distance traveled by a moving particle (such as an atom, a molecule or a photon) between successive impacts (collisions), which modifies its direction, energy or other particle proper...

Mean Free Path Using Electron Density

The mean free path is the average distance traveled by a moving particle (such as an atom, a molecule or a photon) between successive impacts (collisions), which modifies its direction, energy or other particle proper...

Meat Defrosting Time in Water

Thawing time is the time to defrost a food item in a cold-water bath.

Meat Defrosting Time in Air

Thawing time is the time to defrost a food item in the refrigerator.

Mechanical Stress for a Cylinder

The mechanical stress for a cylinder expresses the internal forces that neighboring particles within the cylinder exert on each other.

Mechanical Stresses on a Thin-Walled Hoop

A cylinder stress is a stress distribution with rotational symmetry, one that remains unchanged if the stressed object is rotated about some fixed axis.

Mechanical Stress

Stress is a physical quantity that expresses the internal forces that neighboring particles of a continuous material exert on each other.

Mechanical Advantage of a Wheel and Axle

Mechanical advantage is a measure of the force amplification achieved by using a tool—in this case, a wheel and axle.

Mechanical Advantage of a Wedge by Dimensions

Mechanical advantage is a measure of the force amplification achieved by using a tool, in this case a wedge.

Mechanical advantage is a measure of the force amplification achieved by using a tool, in this case a screw.

Mechanical advantage is a measure of the force amplification achieved by using a tool, in this case a screw.

Mechanical Advantage of a Pulley System

Mechanical advantage is a measure of the force amplification achieved by using a tool—in this case a pulley system.

Mechanical Advantage of an Inclined Plane by Slope

Mechanical advantage is a measure of the force amplification achieved by using a tool, in this case an inclined plane.

Mechanical Advantage of an Inclined Plane by Dimensions

Mechanical advantage is a measure of the force amplification achieved by using a tool, in this case an inclined plane.

Mechanical advantage is a measure of the force amplification achieved by using a tool, in this case a lever.

Minimum Variance Hedge Ratio

The hedge ratio compares the value of a position protected through the use of a hedge with the size of the entire position itself. The minimum variance hedge ratio is important when cross-hedging, which aims to minimi...

Minimum Power Required to Move Object

The minimum power required to move an object depends on the work done and the time it takes to complete the movement.

Modified Internal Rate of Return

The modified internal rate of return is a financial measure of an investment's attractiveness.

Modified Duration of Bonds

Modified duration is the name given to the price sensitivity, and is the percentage change in price for a unit change in yield.

Mohr–Coulomb Failure Criterion

The Mohr–Coulomb failure criterion represents the linear envelope that is obtained from a plot of the shear strength of a material versus the applied normal stress.

Mohr's Circle Plane Shear Stress

Mohr's circle is a two-dimensional graphical representation of the transformation law for the Cauchy stress tensor. Stress is a physical quantity that expresses the internal forces that neighboring particles of a cont...

Mohr's Circle Plane Shear Strain

Mohr's circle is a two-dimensional graphical representation of the transformation law for the Cauchy stress tensor. Strain is a description of deformation in terms of relative displacement of particles in the body tha...

Mohr's Circle Plane Normal Stress Y Direction

Mohr's circle is a two-dimensional graphical representation of the transformation law for the Cauchy stress tensor. Stress is a physical quantity that expresses the internal forces that neighboring particles of a cont...

Mohr's Circle Plane Normal Stress X Direction

Mohr's circle is a two-dimensional graphical representation of the transformation law for the Cauchy stress tensor. Stress is a physical quantity that expresses the internal forces that neighboring particles of a cont...

Mohr's Circle Plane Normal Strain Y Direction

Mohr's circle is a two-dimensional graphical representation of the transformation law for the Cauchy stress tensor. Normal strain is a description of deformation in terms of relative displacement of particles in the n...

Mohr's Circle Plane Normal Strain X Direction

Mohr's circle is a two-dimensional graphical representation of the transformation law for the Cauchy stress tensor. Normal strain is a description of deformation in terms of relative displacement of particles in the n...

Molarity-to-Density Formula

Molar concentration, also called molarity, amount concentration or substance concentration, is a measure of the concentration of a solute in a solution, or of any chemical species, in terms of the amount of substance ...

Momentum Using Velocity

Momentum is the product of the mass and velocity of an object.

Momentum Using Kinetic Energy

Momentum is the product of the mass and velocity of an object.

Moment of Inertia Ratio

The moment of inertia ratio is the ratio of the actual moment of inertia to an object's inertia if it were a point mass.

Moment of Inertia of a Triangular Plate

The mass moment of inertia measures the extent to which an object resists rotational acceleration about a particular axis, and is the rotational analog to mass. For a uniform triangular plate, the moments of inertia a...

Moment of Inertia of a Thin Rod

The parallel and perpendicular moments of inertia of a uniform, infinitely thin rod are taken through its center of mass. The rod is taken to be a one-dimensional wire. In the case of the perpendicular moment of inert...

Moment of Inertia of a Sphere

The mass moment of inertia measures the extent to which an object resists rotational acceleration about a particular axis, and is the rotational analogue to mass. For a uniform solid sphere, the moments of inertia are...

Moment of Inertia of a Point Mass

The mass moment of inertia measures the extent to which an object resists rotational acceleration about a particular axis, and is the rotational analog to mass.

Moment of Inertia of an Elliptical Lamina

The mass moment of inertia measures the extent to which an object resists rotational acceleration about a particular axis, and is the rotational analog to mass. For a uniform elliptical lamina, the moments of inertia ...

Moment of Inertia of an Ellipsoid

The mass moment of inertia measures the extent to which an object resists rotational acceleration about a particular axis, and is the rotational analog to mass. For a uniform solid ellipsoid, the moments of inertia ar...

Moment of Inertia of a Cone

The mass moment of inertia measures the extent to which an object resists rotational acceleration about a particular axis, and is the rotational analog to mass. For a uniform solid cone, the moments of inertia are tak...

Monoprotic Strong Acid-Strong Base Titration

A monoprotic strong acid–base titration is the determination of the concentration of an acid or base by exactly neutralizing the acid or base with an acid or base of known concentration.

Morse Equation

The Morse equation relates osmotic pressure to solute concentration. Osmotic pressure is the minimum pressure that needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane.

Multiple-Slit Diffraction Using Wavenumber

Diffraction refers to various phenomena that occur when a wave encounters an obstacle or a slit. It is defined as the bending of light around the corners of an obstacle or aperture into the region of geometrical shado...

Multiple-Slit Diffraction Using Wavelength

Diffraction refers to various phenomena that occur when a wave encounters an obstacle or a slit. It is defined as the bending of light around the corners of an obstacle or aperture into the region of the geometrical s...

Myth of the Nines Weekly Times

High availability is a characteristic of a system, which aims to ensure an agreed level of operational performance, usually uptime, for a higher-than-normal period. The nines is a measure of this availability, the rat...

Myth of the Nines Monthly Times

High availability is a characteristic of a system, which aims to ensure an agreed level of operational performance, usually uptime, for a higher-than-normal period. The nines is a measure of this availability, the rat...

Myth of the Nines Annual Times

High availability is a characteristic of a system, which aims to ensure an agreed level of operational performance, usually uptime, for a higher-than-normal period. The nines is a measure of this availability, the rat...

N

The uncertainty principle relates the lifetime of an excited state (due to spontaneous radiative decay or the Auger process) with the uncertainty of its energy. A short lifetime will have a large energy uncertainty an...

Negative Predictive Value

The negative predictive value is the proportion of negative results in statistics and diagnostic tests that are true negative results.

Nernst Equation Using Reaction Quotient

The Nernst equation is an equation that relates the reduction potential of an electrochemical reaction (half-cell or full-cell reaction) to the standard electrode potential, temperature and activities (often approxima...

Nernst Equation Using Equilibrium Constant

The Nernst equation is an equation that relates the reduction potential of an electrochemical reaction (half-cell or full-cell reaction) to the standard electrode potential, temperature and activities (often approxima...

Newton's Second Law

In an inertial reference frame, the vector sum of the forces on an object is equal to the mass of that object multiplied by the acceleration of the object.

Newton's Law of Universal Gravitation

Newton's law of universal gravitation states that a particle attracts every other particle in the universe using a force that is directly proportional to the product of their masses and inversely proportional to the s...

Newton's Law of Cooling

Newton's law of cooling states that the rate of heat loss of a body is directly proportional to the difference in the temperatures between the body and its surroundings, provided the temperature difference is small an...

Nijboer–Zernike Aberration

An optical aberration is a departure of the performance of an optical system from the predictions of paraxial optics. The analysis by Nijboer and Zernike describes the intensity distribution close to the optimum focal...

Nominal-to-Effective Rate with Continuous Compounding

The effective interest rate is the interest rate on a loan or financial product restated from the nominal interest rate as an interest rate with annual compound interest payable in arrears.

Nominal-to-Effective Interest Rate

The effective interest rate is the interest rate on a loan or financial product restated from the nominal interest rate as an interest rate with annual compound interest payable in arrears.

Noninverting Amplifier

A noninverting amplifier is an operational amplifier where the output voltage changes in the same direction as the input voltage. An operational amplifier (often op-amp or opamp) is a DC-coupled, high-gain electronic ...

Normalized Frequency

The normalized frequency, or V number, is a parameter used in optical fibers.

Nozzle Air Velocity

The nozzle air velocity describes the speed of air flowing out of a nozzle under pressure. A nozzle is a device designed to control the direction or characteristics of a fluid flow (especially to increase velocity) as...

Numerical Aperture Using f-Number

The numerical aperture of an optical system is a dimensionless number that characterizes the range of angles over which the system can accept or emit light.

Numerical Aperture Using Aperture Diameter

The numerical aperture of an optical system is a dimensionless number that characterizes the range of angles over which the system can accept or emit light.

Nusselt Number

The Nusselt number is the ratio of convective to conductive heat transfer across (normal to) the boundary.

O

Odds Ratio

The odds ratio is a way to quantify how strongly the presence or absence of property A is associated with the presence or absence of property B in a given population.

Ohm's Law

The current through a conductor between two points is directly proportional to the voltage across the two points. It is inversely proportional to the resistance across those two points.

Optimal Throwing Angle

Determine the optimal release angle to maximize distance, assuming no air resistance and a normal Earth-surface gravitational pull using the height of release and the speed of the projectile.

Otto Cycle

An Otto cycle is an idealized thermodynamic cycle that describes the functioning of a typical spark-ignition piston engine.

Oxygen Delivery Using Heart Rate

Oxygen delivery describes the amount of oxygen being distributed through the blood based on arterial oxygen content and the cardiac output.

Oxygen Delivery Using Cardiac Output

Oxygen delivery describes the amount of oxygen being distributed through the blood based on arterial oxygen content and the cardiac output.

Oxygenation Index

The oxygenation index is a calculation used in intensive care medicine to measure the fraction of inspired oxygen and its usage within the body.

P

Page Speed

The page rate or speed is the rate at which pages of a manuscript are read, spoken or written.

Pantoscopic Tilt

Pantoscopic tilt refers to the frame alignment of a lens in the up-and-down position of the glasses frame.

Parallel Resistor-Inductor Circuit

A resistor–inductor circuit is an electric circuit composed of resistors and inductors driven by a voltage or current source. The parallel version places resistor and inductor in parallel.

Parallel Resistor-Inductor Capacitor Circuit

A parallel RLC circuit is an electrical circuit consisting of a resistor, an inductor and a capacitor, connected in parallel.

Parallel Resistor Capacitor Circuit

A resistor–inductor circuit is an electric circuit composed of resistors and capacitors driven by a voltage or current source. The parallel version places resistor and capacitor in parallel.

Parallel Resistance

A circuit composed solely of resistors in parallel is a parallel circuit.

Parallel Capacitance

Parallel capacitance is the capacitance given by two capacitors arranged in parallel.

Parallel Axis Theorem

The parallel axis theorem can be used to determine the mass moment of inertia or the second moment of area of a rigid body about any axis, given the body's moment of inertia about a parallel axis through the object's ...

Parallax Distance

Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semiangle of inclination between those two lines. It can be use...

Paschen's Law

Paschen's law is an equation that gives the breakdown voltage—that is, the voltage necessary to start a discharge or electric arc between two electrodes in a gas as a function of pressure and gap length.

Péclet Number Using Thermal Diffusivity

The Péclet number is a class of dimensionless numbers relevant in the study of transport phenomena in a continuum. It is defined to be the ratio of the rate of advection of a physical quantity by the flow to the rate ...

Péclet Number for Mass Transfer

The Péclet number is a class of dimensionless numbers relevant in the study of transport phenomena in a continuum. It is defined to be the ratio of the rate of advection of a physical quantity by the flow to the rate ...

Pendulum Harmonic Oscillator

A pendulum harmonic oscillator is a pendulum that, when displaced from its equilibrium position, experiences a restoring force proportional to the displacement.

Pendulum

A simple pendulum is an isolated system that assumes a massless, inextensible and taut cord; a point mass weight at the end, with motion occurring only in two dimensions; no friction or air resistance; a uniform gravi...

Perfectly Inelastic Collision

An inelastic collision is a collision in which kinetic energy is not conserved due to the action of internal friction. A perfectly inelastic collision occurs when the maximum amount of kinetic energy of a system is lo...

Perpetuity

A perpetuity is an annuity in which the periodic payments begin on a fixed date and continue indefinitely.

Phase Speed of Water Wave

The phase speed of a water wave is the rate at which the phase of the wave propagates through the water.

Photon Wavenumber Using Wavelength

A photon is an elementary particle, the quantum of the electromagnetic field including electromagnetic radiation (such as light) and the force carrier for the electromagnetic force.

Photon Momentum Using Wavenumber

A photon is an elementary particle, the quantum of the electromagnetic field including electromagnetic radiation (such as light) and the force carrier for the electromagnetic force. The momentum of a photon depends on...

Photon Momentum Using Wavelength

A photon is an elementary particle, the quantum of the electromagnetic field including electromagnetic radiation (such as light) and the force carrier for the electromagnetic force. The momentum of a photon depends on...

Photon Momentum Using Frequency

A photon is an elementary particle, the quantum of the electromagnetic field including electromagnetic radiation (such as light) and the force carrier for the electromagnetic force. The momentum of a photon depends on...

Photon Frequency Using Wavelength

A photon is an elementary particle, the quantum of the electromagnetic field including electromagnetic radiation (such as light) and the force carrier for the electromagnetic force.

Photon Energy Using Wavelength

A photon is an elementary particle, the quantum of the electromagnetic field including electromagnetic radiation (such as light) and the force carrier for the electromagnetic force. The energy of a photon depends only...

Photon Energy Using Frequency

A photon is an elementary particle, the quantum of the electromagnetic field including electromagnetic radiation (such as light) and the force carrier for the electromagnetic force. The energy of a photon depends only...

Photon Energy Using Angular Frequency

A photon is an elementary particle, the quantum of the electromagnetic field including electromagnetic radiation (such as light) and the force carrier for the electromagnetic force. The energy of a photon depends only...

pH Using pOH

pH, the potential of hydrogen, is a numeric scale used to specify the acidity or basicity of an aqueous solution.

pKa Using Concentrations

An acid dissociation constant is a quantitative measure of the strength of an acid in solution. pKa refers to the logarithm of the acid dissociation constant.

pKa Using Acidity Constant

An acid dissociation constant is a quantitative measure of the strength of an acid in solution. pKa refers to the logarithm of the acid dissociation constant.

Planck's law describes the spectral density of electromagnetic radiation emitted by a blackbody in thermal equilibrium at a given temperature.

Planck's law describes the spectral density of electromagnetic radiation emitted by a blackbody in thermal equilibrium at a given temperature.

pOH

pOH, the potential of hydroxide ions, is a numeric scale used to specify the acidity or basicity of an aqueous solution.

Poisson Ratio

Poisson's ratio is the signed ratio of transverse strain to axial strain.

Polytropic Process

A polytropic process is a thermodynamic process that obeys the relation that the pressure times the specific volume to the power of the polytropic index equals a constant.

Pooled Variance

Pooled variance is a method for estimating the variance of several different populations when the mean of each population may be different, but one may assume that the variance of each population is the same.

Pooled Standard Deviation

Pooled standard deviation is the square root of the pooled variance. Pooled variance is a method for estimating the variance of several different populations when the mean of each population may be different, but one ...

Positive Predictive Value

The positive predictive value is the proportion of positive results in statistics and diagnostic tests that are true positive results.

Power Factor Using Voltage

The power factor of an AC electrical power system is defined as the ratio of the real power flowing to the load to the apparent power in the circuit.

Power Factor Using Electric Apparent Power

The power factor of an AC electrical power system is defined as the ratio of the real power flowing to the load to the apparent power in the circuit.

Power Exerted on a Rotating Object

Torque is a rotational force. Torque acting through a rotational distance over time creates power.

Prandtl Number Using Thermal Diffusivity

The Prandtl number is a dimensionless number defined as the ratio of momentum diffusivity to thermal diffusivity.

Prandtl Number Using Thermal Conductivity

The Prandtl number is a dimensionless number defined as the ratio of momentum diffusivity to thermal diffusivity.

Present Value of Annuity Due

An annuity is a series of payments made at equal intervals. An annuity due is an annuity whose payments are made at the beginning of each period. The present value of an annuity is the value of a stream of payments, d...

Present Value of Annuity

An annuity is a series of payments made at equal intervals. The present value of an annuity is the value of a stream of payments, discounted by the interest rate to account for the fact that payments are being made at...

Present and Future Value with Continuous Compounding

Future value is the value of an asset at a specific date, assuming a certain interest rate, or more generally, rate of return.

Present and Future Value

Future value is the value of an asset at a specific date, assuming a certain interest rate or, more generally, rate of return.

Pressure of a Column of Fluid

The pressure of a column of fluid depends on the surface pressure and the depth of the column.

Pressure Formula

Pressure is the force applied perpendicular to the surface of an object per unit area over which that force is distributed.

Prevalence

Prevalence is the true proportion of a disease in a population.

Principal Stresses

At every point in a stressed body, there are at least three planes, called principal planes, with normal vectors, called principal directions, where the corresponding stress vector is perpendicular to the plane, i.e. ...

Principal and Interest Using Principal Part

Principal is the amount on which the issuer pays interest, and which, most commonly, has to be repaid at the end of the term.

Principal and Interest Using Interest Part

Principal is the amount on which the issuer pays interest, and which, most commonly, has to be repaid at the end of the term.

Prism Refraction

A prism is a transparent optical element with flat, polished surfaces that refract light. At least two of the flat surfaces must have an angle between them, called the apex angle.

Probability of the Union of Two Events

The probability of the union of two events depends on the probability of either event and the probability of only one of the events occuring.

Probability of Exceedance

The frequency of exceedance, sometimes called the annual rate of exceedance, is the number of times in a certain period that a random process exceeds some critical value.

Projectile Slant Range

A projectile is any object thrown into space (empty or not) by the exertion of a force. The projectile slant range describes the final distance of that projectile under the influence of gravity along a nonhorizontal s...

Projectile Path

A projectile is any object thrown into space (empty or not) by the exertion of a force. The projectile path describes the trajectory of that projectile under the influence of gravity.

Proper Velocity Using Rapidity

Proper velocity, also known as celerity, is an alternative to velocity for measuring motion. Whereas velocity relative to an observer is distance per unit time where both distance and time are measured by the observer...

Proper Velocity

Proper velocity, also known as celerity, is an alternative to velocity for measuring motion. Whereas velocity relative to an observer is distance per unit time where both distance and time are measured by the observer...

Pythagorean Theorem

The Pythagorean theorem is a fundamental relation in Euclidean geometry among the three sides of a right triangle. It states that the square of the hypotenuse (the side opposite the right angle) is equal to the sum of...

Q

A quadratic equation is any equation having the form a x^2 + b x + c = 0.

R

The horizon or skyline is the apparent line that separates earth from sky, the line that divides all visible directions into two categories: those that intersect the Earth's surface, and those that do not. The radio h...

RAID Array

RAID (redundant array of independent disks) is a data storage virtualization technology that combines multiple physical disk drive components into a single logical unit for the purposes of data redundancy, performance...

Rainbow Altitude

A rainbow is a meteorological phenomenon that is caused by reflection, refraction and dispersion of light in water droplets, resulting in a spectrum of light appearing in the sky. It takes the form of a multicolored a...

Rankine Cycle

The Rankine cycle is a model that is used to predict the performance of steam turbine systems, though the theoretical principle also applies to reciprocating engines such as steam locomotives. The Rankine cycle is an ...

Raoult's Law Using Partial Pressures

Raoult's law is a law of thermodynamics that states that the partial vapor pressure of each component of an ideal mixture of liquids is equal to the vapor pressure of the pure component multiplied by its mole fraction...

Rapidity

Rapidity is commonly used as a measure for relativistic velocity. Mathematically, rapidity can be defined as the hyperbolic angle that differentiates two frames of reference in relative motion, each frame being associ...

Rayleigh Scattering Cross-Section for Particles

Rayleigh scattering is the elastic scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of the radiation.

Rayleigh Scattering Cross-Section for Molecules of Gases

Rayleigh scattering is the elastic scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of the radiation.

Rayleigh Number Using Thermal Diffusivity

The Rayleigh number for a fluid is a dimensionless number associated with buoyancy-driven flow, also known as free convection or natural convection.

Rayleigh Number Using Thermal Conductivity

The Rayleigh number for a fluid is a dimensionless number associated with buoyancy-driven flow, also known as free convection or natural convection.

Rayleigh Flow

Rayleigh flow refers to frictionless, nonadiabatic flow through a constant area duct where the effect of heat addition or rejection is considered.

Rayleigh Criterion Angle for Circular Aperture Diffraction

The diffraction intensity ratio is the ratio between intensity at a given angle and the incident intensity of light passing through a circular aperture.

RC Circuit

A resistor–capacitor circuit (RC circuit) is an electric circuit composed of resistors and capacitors driven by a voltage or current source. The time required for the voltage to fall by a factor of 1/e is called the R...

Real Rate of Return

Rate of return is a profit on an investment over a period of time, expressed as a proportion of the original investment. The real rate of return takes into account the inflation rate.

Rectangular Resonant Cavity Using Resistivity

A microwave cavity or radio frequency (RF) cavity is a special type of resonator consisting of a closed (or largely closed) metal structure that confines electromagnetic fields in the microwave region of the spectrum....

Rectangular Resonant Cavity Using Conductivity

A microwave cavity or radio frequency (RF) cavity is a special type of resonator consisting of a closed (or largely closed) metal structure that confines electromagnetic fields in the microwave region of the spectrum....

Rectangular Dielectric Resonant Cavity Using Conductivity

A microwave cavity or radio frequency (RF) cavity is a special type of resonator consisting of a closed (or largely closed) metal structure that confines electromagnetic fields in the microwave region of the spectrum....

Rectangle Area

A rectangle is a quadrilateral with four right angles. Its area is the space within its borders.

Redlich–Kwong Equation of State

The Redlich–Kwong equation of state is an empirical, algebraic equation that relates temperature, pressure and volume of gases.

Redshift Wavelength

Redshift happens when light or other electromagnetic radiation from an object is increased in wavelength, or shifted to the red end of the spectrum.

Redshift Frequency

Redshift happens when light or other electromagnetic radiation from an object is increased in wavelength, or shifted to the red end of the spectrum.

Reduced Mass

The reduced mass is the \"effective\" inertial mass appearing in the two-body problem of Newtonian mechanics.

Reduced and Spectroscopic Wavenumber

The wavenumber is the spatial frequency of a wave, either in cycles per unit distance or radians per unit distance.

Refractive Index

The refractive index, or index of refraction of a material, is a dimensionless number that describes how light propagates through that medium.

Relativistic Time Dilation

Time dilation is the phenomenon of a slowing of time as measured by an observer who is traveling at any nonzero velocity relative to the object.

Relativistic Redshift

Redshift happens when light or other electromagnetic radiation from an object is increased in wavelength, or shifted to the red end of the spectrum. Relativistic redshift is caused by the relative motion of the source...

Relativistic Momentum

The relativistic momentum is the product of the mass and velocity of an object after a Lorentz transformation.

Relativistic Length Contraction

Length contraction is the phenomenon of a decrease in length of an object as measured by an observer who is traveling at any nonzero velocity relative to the object.

Relativistic Kinetic Energy

The kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity.

Relativistic Energy for Rest Mass

The energy–momentum relation is the relativistic equation relating any object's rest (intrinsic) mass, total energy and momentum. From this, the relativistic energy can be calculated.

Relativistic Energy for Moving Mass

The energy–momentum relation is the relativistic equation relating any object's rest (intrinsic) mass, total energy and momentum. From this, the relativistic energy can be calculated.

Relativistic Doppler Shift Using Wavelength and Observer Speed

The relativistic Doppler effect is the change in the wavelength of light, caused by the relative motion of the source and the observer (as in the classical Doppler effect) when taking into account effects described by...

Relativistic Doppler Shift Using Wavelength

The relativistic Doppler effect is the change in wavelength of light, caused by the relative motion of the source and the observer (as in the classical Doppler effect), when taking into account effects described by th...

Relativistic Doppler Shift Using Frequency and Observer Speed

The relativistic Doppler effect is the change in the frequency of light, caused by the relative motion of the source and the observer (as in the classical Doppler effect) when taking into account effects described by ...

Relativistic Doppler Shift Using Frequency

The relativistic Doppler effect is the change in frequency of light, caused by the relative motion of the source and the observer (as in the classical Doppler effect), when taking into account effects described by the...

Relativistic de Broglie Wavelength by Velocity

The de Broglie wavelength is the wavelength associated with a massive particle in motion according to quantum mechanics, accounting for relativistic effects.

Relativistic de Broglie Wavelength by Kinetic Energy

The de Broglie wavelength is the wavelength associated with a massive particle in motion according to quantum mechanics, accounting for relativistic effects.

Relativistic de Broglie Frequency by Velocity

The de Broglie frequency is the frequency associated with a massive particle in motion according to quantum mechanics, accounting for relativistic effects.

Relativistic de Broglie Frequency by Kinetic Energy

The de Broglie frequency is the frequency associated with a massive particle in motion according to quantum mechanics, accounting for relativistic effects.

Relativistic de Broglie Angular Frequency by Velocity

The de Broglie angular frequency is the angular frequency associated with a massive particle in motion according to quantum mechanics, accounting for relativistic effects.

Relativistic de Broglie Angular Frequency by Momentum

The de Broglie angular frequency is the angular frequency associated with a massive particle in motion according to quantum mechanics, accounting for relativistic effects.

Relativistic de Broglie Angular Frequency by Kinetic Energy

The de Broglie angular frequency is the angular frequency associated with a massive particle in motion according to quantum mechanics, accounting for relativistic effects.

In relativistic physics, a velocity-addition formula is an equation that relates the velocities of objects in different reference frames.

Relativistic Aberration

Relativistic aberration is the relativistic version of aberration of light for observers who move with velocities close to the speed of light. This causes the rays of light from the source that reach the observer to b...

Relative Graham Value

The relative Graham value is a modification of the results of a formula designed by Benjamin Graham for the evaluation of growth stocks.

Renal Failure Index

The renal failure index is used to differentiate between renal and pre-renal acute renal failure.

Resistance Formula

The electrical resistance of an electrical conductor is a measure of the difficulty to pass an electric current through that conductor.

Resonance Frequency Equation

An LC circuit, also called a resonant circuit, is an electric circuit consisting of an inductor and a capacitor connected together. The circuit can act as an electrical resonator (an electrical analog of a tuning fork...

Respiratory Quotient

The respiratory quotient is a dimensionless number used in calculations of basal metabolic rate when estimated from carbon dioxide production. It is calculated from the ratio of carbon dioxide produced by the body to ...

Return on Investment

The return on investment is the benefit to an investor resulting from an investment of some resource.

Revised Benjamin Graham Formula

The Benjamin Graham formula is an intrinsic value formula used to quickly determine how rationally priced stocks were.

Reynolds Number Using Kinematic Viscosity

The Reynolds number is an important dimensionless quantity in fluid mechanics used to help predict flow patterns in different fluid flow situations.

Richardson Number

The Richardson number is the dimensionless number that expresses the ratio of the buoyancy term to the flow shear term.

Richter Scale Magnitude to Energy

The Richter magnitude scale assigns a magnitude number to quantify the size of an earthquake. The Richter scale is a base 10 logarithmic scale, which defines magnitude as the logarithm of the ratio of the amplitude of...

Richter Scale Magnitude

The Richter magnitude scale assigns a magnitude number to quantify the size of an earthquake. The Richter scale is a base 10 logarithmic scale, which defines magnitude as the logarithm of the ratio of the amplitude of...

Rise and Run of Slopes

The grade (also called slope, incline, gradient, mainfall, pitch or rise) of a physical feature, landform or constructed line refers to the tangent of the angle of that surface to the horizontal.

Rolling Motion

Rolling is a type of motion that combines rotation (commonly of an axially symmetric object) and translation of that object with respect to a surface (either one or the other moves), such that, if ideal conditions exi...

Rolling Friction Coefficient

Rolling resistance is the force that resists the rolling of a wheel or other circular object along a surface caused by deformations in the object or surface.

Rossby Number

The Rossby number is a dimensionless number used in describing fluid flow.

Rossiter Coefficient and Frequency

The Rossiter coefficient is related to the Strouhal number, a dimensionless number describing oscillating flow mechanisms. The frequency is the frequency of vortex shedding.

Rotational Kinetic Energy

Rotational kinetic energy, or angular kinetic energy, is kinetic energy due to the rotation of an object and is part of its total kinetic energy.

Rowing Machine Using Pace

An indoor rower, or rowing machine, is a machine used to simulate the action of watercraft rowing for the purpose of exercise or training for rowing.

Rule of 70

The rule of 70 is a method for estimating an investment's doubling time.

Running in the Rain

Running in the rain approximates how wet a person would get from running in the rain.

Rutherford Scattering Scattering Cross-Section

Rutherford scattering is the elastic scattering of charged particles by the Coulomb interaction.

Rydberg Formula

The Rydberg formula is used in atomic physics to describe the wavelengths of spectral lines of many chemical elements.

S

Sackur–Tetrode Equation Using Internal Energy

The Sackur–Tetrode equation is an expression for the entropy of a monatomic classical ideal gas, which incorporates quantum considerations that give a more detailed description of its regime of validity.

Sample Size for Estimating a Population Mean

Sample size determination is the act of choosing the number of observations or replicates to include in a statistical sample.

Sample Size for Estimating a Binomial Parameter

The sample size for estimaitng a binomial parameter estimates the minimum sample size to estimate the binomial parameter.

Schmidt Number Using Dynamic Viscosity

The Schmidt number is a dimensionless number defined as the ratio of momentum diffusivity (kinematic viscosity) and mass diffusivity, and is used to characterize fluid flows in which there are simultaneous momentum an...

Scribner's Log Rule

Scribner's log rule is a tool for use in the estimation of standing timber volume.

Second-Order Arrhenius Equation

The Arrhenius equation is a formula for the temperature dependence of reaction rates.

Second Cowling Number

The Cowling number expresses the magnetic-to-intertia forces ratio.

Seismic Moment Using Rupture Dimensions

Seismic moment is a quantity used by seismologists to measure the size of an earthquake.

Seismic Moment Using Rupture Area

Seismic moment is a quantity used by seismologists to measure the size of an earthquake.

Seismic Moment Magnitude and Equivalent Energy

Seismic moment is a quantity used by seismologists to measure the size of an earthquake. It is directly proportional to the energy released.

Self-Capacitance of Two Identical Spheres in Contact

Self-capacitance is the amount of electric charge that must be added to an isolated conductor to raise its electric potential by one unit.

Self-Capacitance of a Solid Cylinder

Self-capacitance is the amount of electric charge that must be added to an isolated conductor to raise its electric potential by one unit.

Self-Capacitance of a Disk

Self-capacitance is the amount of electric charge that must be added to an isolated conductor to raise its electric potential by one unit.

Self-Inductance of Two Parallel Wires

The self­inductance of two parallel wires is a property that describes the electromotive force caused by the change in current in the wires.

Self-Inductance of a Single-Layer Rectangular Cross-Section Coil

The self­inductance of a single-layer rectangular cross-section coil is a property that describes the electromotive force caused by the change in current in the coil.

Self-Inductance of a Single-Layer Circular Coil of Small Radius

The self­inductance of a single­layer circular coil of small radius is a property that describes the electromotive force caused by the change in current in the coil.

Self-Inductance of a Single-Layer Circular Coil

The self­inductance of a single­layer circular coil is a property that describes the electromotive force caused by the change in current in the coil.

Self-Inductance of a Single Core Cable

The self­inductance of a single core cable is a property that describes the electromotive force caused by the change in current in the cable.

Sensitivity

Sensitivity (also called the true positives rate) measures the proportion of positives that are correctly identified as such (i.e. the percentage of healthy people who are correctly identified as having the condition).

Series RL Circuit

A resistor–inductor circuit (RL circuit) is an electric circuit composed of resistors and inductors driven by a voltage or current source. The time required for the voltage to fall by a factor of 1/e is called the RL ...

Series RLC Circuit

An RLC circuit is an electrical circuit consisting of a resistor, an inductor and a capacitor, connected in series or in parallel.

Series Resistance

A circuit composed solely of resistors in series is a series circuit.

Series Capacitance

Series capacitance is the capacitance given by two capacitors arranged in series.

Serum Osmolarity

Serum osmolarity measures the body's electrolyte-water balance.

Simple Interest

Interest is payment from a borrower or deposit-taking financial institution to a lender or depositor of an amount above repayment of the principal sum (i.e. the amount borrowed). Simple interest is calculated only on ...

Simple Boiling-Point Elevation Equation

Boiling-point elevation describes the phenomenon that the boiling point of a liquid (a solvent) will be higher when another compound is added, meaning that a solution has a higher boiling point than a pure solvent. Th...

Single-Slit Diffraction Using Wavenumber and Rayleigh Criterion Angle

Single­slit diffraction occurs when light passes through a narrow slit and creates an interference pattern on the other side.

Single-Slit Diffraction Using Wavenumber and Intensity Ratio

Single­slit diffraction is when light passes through a narrow slit and creates an interference pattern on the other side.

Single-Slit Diffraction Using Wavelength and Rayleigh Criterion Angle

Single­slit diffraction occurs when light passes through a narrow slit and creates an interference pattern on the other side.

Single-Slit Diffraction Using Wavelength and Intensity Ratio

Single­slit diffraction is when light passes through a narrow slit and creates an interference pattern on the other side.

Slant Range to Aircraft

Slant range is the line-of-sight distance between two points (in this case, one point is an aircraft) that are not at the same level relative to a specific datum.

Slope of a Line

The slope or gradient of a line is a number that describes both the direction and the steepness of the line.

Small-Oscillation Pendulum

A simple pendulum is an isolated system that assumes a massless, inextensible and taut cord; a point mass weight at the end, with motion occurring only in two dimensions; no friction or air resistance; a uniform gravi...

Snell's Law

Snell's law is a formula used to describe the relationship between the angles of incidence and refraction, when referring to light or other waves passing through a boundary between two different isotropic media.

Sodium Deficit

Sodium deficit is the measure of the sodium in the patient's blood to the ideal amount.

Specificity

Specificity (also called the true negative rate) measures the proportion of negatives that are correctly identified as such (i.e. the percentage of healthy people who are correctly identified as not having the conditi...

Speed of Sound in an Ideal Gas by Temperature and Molar Mass

The speed of sound is the distance traveled per unit time by a sound wave as it propagates through an elastic medium.

Speed of Sound in an Ideal Gas by Temperature and Mass of Molecule

The speed of sound is the distance traveled per unit time by a sound wave as it propagates through an elastic medium.

Speed of Sound in an Ideal Gas by Pressure

The speed of sound is the distance traveled per unit time by a sound wave as it propagates through an elastic medium.

Speed under Constant Acceleration

The speed of an object is the magnitude of its velocity (the rate of change of its position).

Spherical Law of Tangents

The spherical law of tangents is a statement about the relationship between the tangents of two angles of a triangle on a sphere and the angular lengths of the opposing sides.

Spherical Law of Sines

The spherical law of sines is an equation relating the angular lengths of the sides of a triangle (any shape) to the sines of its angles.

Spherical Law of Cosines Using Angles

The spherical law of cosines is a theorem relating the sides and angles of spherical triangles, analogous to the ordinary law of cosines from plane trigonometry.

Spheroid Volume

A spheroid is a solid generated by a half-revolution of an ellipse about its major axis (prolate spheroid) or minor axis.

Spot Image Size Using Focal Length

If two objects imaged by a camera are separated by an angle small enough that their Airy disks on the camera detector start overlapping, the objects cannot be clearly separated any more in the image, and they start bl...

Spot Image Size Using f-Number

If two objects imaged by a camera are separated by an angle small enough that their Airy disks on the camera detector start overlapping, the objects cannot be clearly separated any more in the image, and they start bl...

Spring Harmonic Oscillator

A spring harmonic oscillator is a spring that, when displaced from its equilibrium position, experiences a restoring force proportional to the displacement.

Spring Constant for Helical Spring

The spring constant is the stiffness of a spring—the force needed to stretch it a certian distance.

Stair Climbing

Stair climbing is the climbing of a flight of stairs.

Stanton Number

The Stanton number is a dimensionless number that measures the ratio of heat transferred into a fluid to the thermal capacity of fluid.

Static Friction Coefficient Using Friction Force

Static friction is a force that opposes the relative lateral motion of two solid non-moving surfaces in contact.

Stefan–Boltzmann Law

The Stefan–Boltzmann law describes the power radiated from a blackbody in terms of its temperature. Specifically, the Stefan–Boltzmann law states that the total energy radiated per unit surface area of a blackbody acr...

Stirling Cycle for a Heat Pump

The Stirling cycle is a thermodynamic cycle that describes the general class of Stirling devices.

Stirling Cycle for a Heat Engine

The Stirling cycle is a thermodynamic cycle that describes the general class of Stirling devices.

Stock Contracts Optimal Number

The optimal futures contracts number is the optimal number of contracts needed to hedge a position. It is calculated by dividing the product of the optimal hedge ratio and the units of the position being hedged by the...

Strehl Ratio

The Strehl ratio is a measure of the quality of optical image formation.

Strouhal Number

The Strouhal number is a dimensionless number describing oscillating flow mechanisms.

Subject Magnification

The subject magnification factor is how much the subject is enlarged.

Suratman Number

The Suratman number is a dimensionless number used in the characterization of free-surface fluid dynamics. It represents a ratio of surface tension to the momentum transport (especially dissipation) inside a fluid.

Sutherland's Formula

Sutherland's formula can be used to derive the dynamic viscosity of an ideal gas as a function of the temperature.

Swelling Interface Number

The swelling interface number is important in describing the relationship between solvent penetration and solute diffusion.

Synchronous Speed

An electric motor is an electrical machine that converts electrical energy into mechanical energy. A synchronous electric motor is an AC motor distinguished by a rotor spinning with coils passing magnets at the same r...

T

Turkey Portion Counter

The Turkey Portion Counter calculates the turkey mass needed to feed a group of adults, teenagers and children.

Telescope Magnifying Power

The magnification through a telescope magnifies a viewing object while limiting the field of view.

Telescope Light-Gathering Power

The light-gathering power of an optical telescope, also referred to as light grasp or aperture gain, is the ability of a telescope to collect a lot more light than the human eye.

Doppler broadening is the broadening of spectral lines due to the Doppler effect, caused by a distribution of thermal velocities of atoms or molecules.

Doppler broadening is the broadening of spectral lines due to the Doppler effect, caused by a distribution of thermal velocities of atoms or molecules.

Thermal Deformation

Thermal deformation refers to any changes in the shape or size of an object due to a change in temperature.

Thermodynamic Energy

In thermodynamics, the internal energy of a system is the energy contained within the system, excluding the kinetic energy of motion of the system as a whole and the potential energy of the system as a whole due to ex...

Thin Lens Equation

The thin lens formula relates the distances from the object to the lens and from the lens to the image to the focal length for a lens of negligible thickness in air.

Torque Using Moment of Inertia

Torque is a rotational force.

Torricelli's Theorem

Torricelli's law, also known as Torricelli's theorem, is a theorem in fluid dynamics relating the speed of fluid flowing out of an orifice to the height of fluid above the opening. The law states that the speed of eff...

Torsion Angle of Twist

Torsion is the twisting of an object due to an applied torque.

Torus Volume

A torus is a surface of revolution generated by revolving a circle in three-dimensional space about an axis coplanar with the circle. The volume is the space contained within the resulting surface.

Total Internal Reflection

Total internal reflection is the phenomenon that occurs when a propagated wave strikes a medium boundary at an angle larger than a particular critical angle with respect to the normal to the surface.

The transtubular potassium gradient is an index reflecting the conservation of potassium in the cortical collecting ducts of the kidneys.

Trapezoid Area

A convex quadrilateral with at least one pair of parallel sides is referred to as a trapezoid. The parallel sides are called the bases of the trapezoid, and the other two sides are called the legs or the lateral sides...

Triangle Area Using Base and Height

A triangle is a polygon with three edges and three vertices. The area is the space enclosed by the triangle.

Turkey Frying Time

The turkey frying time is the time needed to properly fry a turkey.

Turkey Cooking Time

The turkey cooking time is the time needed to properly cook a turkey.

Two Infinitely Long Parallel Wires

Currents passing through two infinitely long parallel wires create a magnetic force between the two.

V

Van der Waals Equation

The van der Waals equation is a thermodynamic equation of state that is based on the theory that fluids are composed of particles with nonzero volumes, and subject to a (not necessarily pairwise) interparticle attract...

Vector Projection

The vector projection of a vector a on (or onto) a nonzero vector b (also known as the vector component or vector resolution of a in the direction of b) is the orthogonal projection of a onto a straight line parallel ...

Velocity Components

The velocity of an object is the rate of change of its position with respect to a frame of reference. Its components are the portions of the velocity in the direction of the coordinate system vectors.

Vickers Hardness

The Vickers hardness test was developed as an alternative to the Brinell method to measure the hardness of materials. The Vickers test is often easier to use than other hardness tests, since the required calculations ...

Viscosity Conversion Formula

The kinematic viscosity is the ratio of the dynamic viscosity μ to the density of the fluid.

W

Words per Page of a Manuscript

This formula describes the approximate relationship between pages and words in a manuscript.

Words per Page of a Magazine

This formula describes the approximate relationship between pages and words in a magazine.

Words per Page of a Book

This formula describes the approximate relationship between pages and words in a book.

Water Hammer Pressure with Slow Closure

Water hammer (or, more generally, fluid hammer) is a pressure surge or wave caused when a fluid (usually a liquid but sometimes also a gas) in motion is forced to stop or change direction suddenly (momentum change). A...

Water Hammer Pressure with Fast Closure

Water hammer (or, more generally, fluid hammer) is a pressure surge or wave caused when a fluid (usually a liquid, but sometimes also a gas) in motion is forced to stop or change direction suddenly (momentum change). ...

Wave Propagation in Strings

The velocity of propagation of a wave in a string is proportional to the square root of the force of tension of the string, and inversely proportional to the square root of the linear density of the string.

Weber Number

The Weber number is a dimensionless number in fluid mechanics that is often useful in analyzing fluid flows where there is an interface between two different fluids, especially for multiphase flows with strongly curve...

Weighted Average Cost of Capital

The weighted average cost of capital is the rate that a company is expected to pay on average to all its security holders to finance its assets.

Wind Turbine Power

A wind turbine is a device that converts the wind's kinetic energy into electrical energy.

Word Rate

The word rate is the speed at which words are written.

Y

Young's Modulus

Young's modulus, also known as the elastic modulus, is a measure of the stiffness of a solid material. It is a mechanical property of linear elastic solid materials. It defines the relationship between stress (force p...

Z

Zeiss Formula

The Zeiss formula is a supposed formula for computing a circle of confusion criterion for depth-of-field calculations.