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Physical Quantities

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A physical quantity is a physical property of a phenomenon, body, or substance, that can be quantified by measurement.[1] A physical quantity can be expressed as the combination of a magnitude expressed by a number – usually a real number – and a unit; for example, 1.6749275×10−27 kg (the mass of the neutron), or 299792458 metres per second (the speed of light). Physical quantities are measured as n u {\textstyle nu} {\textstyle nu} where {\textstyle n} is the magnitude and {\textstyle u} is the unit. For example: A boy measured the length of a room as 3 m. Here 3 is the magnitude and m (metre) is the unit. 3 m can also be written as 300 cm. The same physical quantity {\textstyle x} can be represented equivalently in many unit systems, i.e. {\textstyle x=n_{1}u_{1}=n_{2}u_{2}}.



Base quantity Symbol Description SI unit Symbol for dimension Comments
Length l The one-dimensional extent of an object. metre (m) L  
Mass m The amount of matter in an object. kilogram (kg) M extensive, scalar
Time t The duration of an event. second (s) T scalar
Electric current I Rate of flow of electrical charge. ampere (A) I  
Temperature T Average energy per degree of freedom of a system. kelvin (K) Θ intensive, scalar
Amount of substance n Number of particles compared to the number of atoms in 0.012 kg of 12C. mole (mol) N extensive, scalar
Luminous intensity L Amount of energy emitted by a light source in a particular direction. candela (cd) J scalar

This list is incomplete; you can help by expanding it.

Derived quantity  
Description SI units Dimension Comments
Plane angle θ Measure of a change in direction or orientation. radian (rad) 1  
Solid angle Ω Measure of the size of an object as projected on a sphere. steradian (sr) 1  
Absorbed dose rate  
Absorbed dose received per unit of time. Gy s−1 L2T−3  
Acceleration a Rate of change of the speed or velocity of an object. m s−2 L T−2 vector
Angular acceleration α Rate of change in angular speed or velocity. rad s−2 T−2  
Angular speed (or angular velocity) ω The angle incremented in a plane by a segment connecting an object and a reference point per unit time. rad s−1 T−1 scalar or pseudovector
Angular momentum L Measure of the extent and direction an object rotates about a reference point. kg m2 s−1 M L2T−1 conserved quantity, pseudovector
Area A The two-dimensional extent of an object. m2 L2 scalar
Area density ρA The amount of mass per unit area of a two-dimensional object. kg m−2 M L−2  
Capacitance C Measure for the amount of stored charge for a given potential. farad (F = A2 s4 kg−1 m−2) I2T4M−1L−2 scalar
Catalytic activity  
Change in reaction rate due to presence of a catalyst. katal (kat = mol s−1) N T−1  
Catalytic activity concentration  
Change in reaction rate due to presence of a catalyst per unit volume of the system. kat m−3 N L−3T−1  
Chemical potential μ The amount of energy needed to add a particle to a system. J mol−1 M L2T−2N−1 intensive
Molar concentration C Amount of substance per unit volume. mol m−3 N L−3 intensive
Crackle c Rate of change of Jounce. The fifth derivative of position. m s−5 L T−5 Vector
Current density J Amount of electric current flowing through a surface. A m−2 I L−2 vector
Dose equivalent H Measure for the received amount of radiation adjusted for the effect of different types of radiant on biological tissue. sievert (Sv = m2 s−2) L2T−2  
Dynamic Viscosity η Measure for the resistance of an incompressible fluid to stress. Pa s M L−1T−1  
Electric Charge Q Amount of electric charge. coulomb (C = A s) I T extensive, conserved quantity
Electric charge density ρQ Amount of electric charge per unit volume. C m−3 I T L−3 intensive
Electric displacement D Strength of the electric displacement. C m−2 I T L−2 vector field
Electric field strength E Strength of the electric field. V m−1 M L T−3I−1 vector field
Electrical conductance G Meausure for how easily current flows through a material. siemens (S = A2 s3 kg−1 m−2) L−2M−1T3I2 scalar
Electric potential V The amount of work required to bring a unit charge into an electric field from infinity. volt (V = kg m2 A−1 s−3) L2M T−3I−1 scalar
Electrical resistance R The degree to which an object opposes the passage of an electric current. ohm (Ω = kg m2 A−2 s−3) L2M T−3I−2 scalar
Energy E The capacity of a body or system to do work. joule (J = kg m2 s−2) M L2T−2 extensive, scalar, conserved quantity
Energy density ρE Amount of energy per unit volume. J m−3 M L−1T−2 intensive
Entropy S Measure for the amount of available states for a system. J K−1 M L2T−2Θ−1 extensive, scalar
Force F The cause of acceleration, acting on an object. newton (N = kg m s−2) M L T−2 vector
Fuel efficiency  
Distance traveled per meter cubed.  
L−2 scalar
Impulse p The cause of a change in momentum, acting on an object. kg m s−1 M L T−1 vector
Frequency f The number of times something happens in a period of time. hertz (Hz =s−1) T−1 scalar
Half-life t1/2 The time needed for a quantity to decay to half its original value. s T  
Heat Q Amount of energy transferred between systems due to temperature difference. J M L2T−2  
Heat capacity Cp Amount of energy needed to raise the temperature of a system by one degree. J K−1 M L2T−2Θ−1 extensive
Heat flux density ϕQ Amount of heat flowing through a surface per unit area. W m−2 M T−3  
Illuminance Ev Total luminous flux incident to a surface per unit area. lux (lx = cd sr m−2) J L−2  
Impedance Z Measure for the resistance of an electrical circuit against an alternating current. ohm (Ω = kg m2 A−2 s−3) M'L'2T−3I−2 complex scalar
Index of refraction n The factor by which the speed of light is reduced in a medium.  
1 intensive, scalar
Inductance L Measure for the amount of magnetic flux generated for a certain current run through a circuit. henry (H = kg m2 A−2 s−2) M L2T−2I−2 scalar
Irradiance E Power of electromagnetic radiation flowing through a surface per unit area. W m−2 M T−3  
Intensity I Power per unit cross sectional area. W m−2 M T−3  
Jerk j Rate of change of acceleration. The third derivative of position. m s−3 L T−3 Vector
Jounce (or snap) s Rate of change of Jerk. The fourth derivative of position. m s−4 L T−4 Vector
Linear density ρl Amount of mass per unit length of a one-dimensional object.  
M L−1  
Luminous flux (or luminous power) F Perceived power of a light source. lumen (lm = cd sr) J  
Mach Number (or mach) M Ratio of flow velocity to the local speed of sound. Unitless (M = u/c) 1  
Magnetic field strength H Strength of a magnetic field in a material. A m−1 I L−1 vector field
Magnetic flux Φ Measure of quantity of magnetism, taking account of the strength and the extent of a magnetic field. weber (Wb = kg m2 A−1 s−2) M L2T−2I−1 scalar
Magnetic flux density B Measure for the strength of the magnetic field. tesla (T = kg A−1 s−2) M T−2I−1 pseudovector field
Magnetization M Amount of magnetic moment per unit volume. A m−1 I L−1 vector field
Mass fraction x Mass of a substance as a fraction of the total mass. kg/kg 1 intensive
(Mass) Density (or volume density) ρ The amount of mass per unit volume of a three-dimensional object. kg m−3 M L−3 intensive
Mean lifetime τ Average time needed for a particle to decay. s T intensive
Molar energy  
Amount of energy present is a system per unit amount of substance. J mol−1 M L2T−2N−1 intensive
Molar entropy  
Amount of entropy present in a system per unit amount of substance. J K−1 mol−1 M L2T−2Θ−1N−1 intensive
Molar heat capacity c Heat capacity of a material per unit amount of substance. J K−1 mol−1 M L2T−2N−1 intensive
Moment of inertia I Inertia of an object with respect to angular acceleration. kg m2 M L2 tensor, scalar
Momentum p Product of an object's mass and velocity. N s M L T−1 vector, extensive
Permeability μ Measure for how the magnetization of material is affected by the application of an external magnetic field. H m−1 M L T−2I−2 intensive
Permittivity ε Measure for how the polarization of a material is affected by the application of an external electric field. F m−1 I2M−1L−3T4 intensive
Power P The rate of change in energy over time. watt (W) M L2T−3 extensive, scalar
Pressure p Amount of force per unit area. pascal (Pa = kg m−1 s−2) M L−1T−2 intensive, scalar
Pop p Rate of change of crackle. The sixth derivative of position. m s−6 L T−6 Vector
(Radioactive) Activity A Number of particles decaying per unit time. becquerel (Bq = s−1) T−1 extensive, scalar
(Radioactive) Dose D Amount of energy absorbed by biological tissue from ionizing radiation per unit mass. gray (unit) (Gy = m2 s−2) L2T−2  
Radiance L Power of emitted electromagnetic radiation per solid angle and per projected source area. W m−2 sr−1 M T−3  
Radiant intensity I Power of emitted electromagnetic radiation per solid angle. W sr−1 M L2T−3 scalar
Reaction rate r Measure for speed of a chemical reaction. mol m−3 s−1 N L−3T−1 intensive, scalar
Refractive Index n Measure of how light is refracted through a medium. Unitless Dimensionless  
Angle θ The space between two intersecting lines at or close to the point where they meet. rad / Degree Dimensionless  
Speed v Rate of change of the position of an object. m s−1 L T−1 scalar
Specific energy  
Amount of energy present per unit mass. J kg−1 L2T−2 intensive
Specific heat capacity c Heat capacity per unit mass. J kg−1 K−1 L2T−2Θ−1 intensive
Specific volume v The volume occupied by a unit mass of material (reciprocal of density). m3 kg−1 L3M−1 intensive
Spin S Intrinsic property of particles, roughly to be interpreted as the intrinsic angular momentum of the particle. kg m2 s−1 M L2T−1  
Extension per unit length. Unitless Dimensionless  
Stress σ Amount of force exerted per surface area. Pa M L−1T−2 2-tensor. (or scalar)
Surface tension γ Amount of work needed to change the surface of a liquid by a unit surface area. N m−1 or J m−2 M T−2  
Thermal conductivity k Measure for the ease with which a material conducts heat. W m−1 K−1 M L T−3Θ−1 intensive
Torque τ Product of a force and the perpendicular distance of the force from the point about which it is exerted. N m M L2T−2 pseudovector
Velocity v Speed of an object in a chosen direction. m s−1 L T−1 vector
Volume V The three dimensional extent of an object. m3 L3 extensive, scalar
Wavelength λ Distance between repeating units of a propagating wave. m L  
Wavenumber k Reciprocal of the wavelength. m−1 L−1  
Weight w Amount of gravitation force exerted on an object. newton (N = kg m s−2) M L T−2 vector
Work W Energy dissipated by a force moving over a distance, scalar product of the force and the movement vector. joule (J = kg m2 s−2) M L2T−2 scalar
Young's modulus ε Ratio of Stress over Strain. pascal (Pa = kg m−1 s−2) M L−1T−2 scalar
Absement A Measure of sustained displacement; the first integral of displacement. m s LT vector

Unit For a Physical quantity

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`    ► Acceleration‎ (3 C, 23 P)
    ► Amount of substance‎ (2 C, 26 P)
    ► Area‎ (3 C, 34 P)
`    ► Capacitance‎ (2 C, 6 P)
    ► Physical constants‎ (3 C, 37 P)
`    ► Density‎ (2 C, 38 P)
`    ► Electric charge‎ (1 C, 7 P)
    ► Electrical resistance and conductance‎ (6 C, 16 P)
    ► Enthalpy‎ (15 P)
    ► Entropy‎ (3 C, 19 P, 1 F)
    ► Thermodynamic entropy‎ (1 C, 40 P)
`    ► Force‎ (8 C, 69 P)
`    ► Geometric measurement‎ (4 C, 12 P)
`    ► Length‎ (6 C, 30 P)
    ► Logarithmic scales of measurement‎ (1 C, 25 P)
`    ► Mass‎ (6 C, 67 P)
    ► Molar quantities‎ (2 P)
`    ► Power (physics)‎ (7 C, 17 P)
    ► Pressure‎ (7 C, 31 P)
`    ► Rates‎ (6 C, 67 P)
`    ► Sound measurements‎ (33 P)
`    ► Temperature‎ (8 C, 61 P)
    ► Time‎ (29 C, 55 P)
`    ► Velocity‎ (4 C, 21 P)
    ► Viscosity‎ (2 C, 32 P)
    ► Visibility‎ (2 C, 23 P)
    ► Voltage‎ (5 C, 10 P)
    ► Volume‎ (4 C, 22 P)


`    ANSI/ASA S1.1-2013
    International System of Quantities
    ISO 31
    ISO/IEC 80000
    List of physical quantities
    Physical quantity
    Quantity calculus
`    Absorbed dose
    Acoustic impedance
    Aggregate modulus
    Angular acceleration
    Angular diameter distance
    Angular frequency
    Angular momentum
    Angular velocity
    API gravity
    Areal velocity
    Attenuation coefficient
    Audio frequency
`    Bollard pull
    Bulk modulus
`    Capacitance
    Characteristic admittance
    Characteristic property
    Charge (physics)
    Circular dichroism
    Cohesion (chemistry)
    Comoving distance
    Conductance quantum
    Couple (mechanics)
`    Defining equation (physics)
    Delta-v (physics)
    Displacement (fluid)
    Distance measures (cosmology)
    Distance modulus
    Dust resistant
    Dynamic modulus
`    Effective dose (radiation)
    Effective radius
    Electric charge
    Electric field
    Electric flux
    Electric intensity
    Electric potential
    Electric susceptibility
    Electrical measurements
    Electrical mobility
    Electrical resistance and conductance
    Electrical resistivity and conductivity
    Electrochemical gradient
    Electron mobility
    Energy flux
    Equivalent dose
    Etherington's reciprocity theorem
    Excess molar quantity
    Extracellular field potential
`    Fermi acceleration
    Field strength
    Film speed
    Fuel efficiency
`    Gravity (chemistry)
    Ground pressure
    Group velocity
`    Heat capacity
    Heat capacity rate
    Heat capacity ratio
    Huber's equation
    Critical relative humidity
    Relative humidity
`    Illuminance
    Electrical impedance
    Characteristic impedance
    Impulse (physics)
    Infinitesimal strain theory
    Intensity (physics)
    Intensive and extensive properties
    Ion transport number
    Ionic strength
`    Jerk (physics)
`    Length
    List of electromagnetism equations
    List of equations in fluid mechanics
    List of equations in gravitation
    List of equations in nuclear and particle physics
    List of equations in quantum mechanics
    List of equations in wave theory
    List of materials properties
    List of moments of inertia
    List of photonics equations
    Luminosity distance
    Luminosity function
    Luminous efficacy
    Luminous energy
    Luminous flux
    Luminous intensity
`    Magnetic braking
    Magnetic field
    Magnetic flux
    Magnetic helicity
    Magnetic hysteresis
    Magnetic moment
    Magnetic susceptibility
    Magnetomotive force
    Mass attenuation coefficient
    Mass flux
    Maximum density
    Measured quantity
    Mechanical impedance
    Mechanical load
    Molar volume
    Molecular property
    Moment (physics)
    Moment of inertia
`    Negative resistance
    Neutron magnetic moment
    Noise-equivalent flux density
    Noise-equivalent target
    Notch tensile strength
    Number density
`    Ohm metre
    Orders of magnitude (speed)
`    Particle displacement
    Particle number
    Particle velocity
    Permeability (electromagnetism)
    Persistence length
    Phase (waves)
    Physical coefficient
    Physical property
    Pinning points
    Plastic crystal
    Poisson's ratio
    Propagation constant
`    Quality (physics)
    Quantum efficiency
    Quartz crystal microbalance with dissipation monitoring
`    Radiance
    Radiant energy density
    Radiant exitance
    Radiant exposure
    Radiant flux
    Radiant intensity
    Radiative flux
    Radiosity (radiometry)
    Rate of penetration
    Electrical reactance
    Reciprocal length
    Refractive index
    Relative density
    Relative velocity
    Rotational speed
`    Scale of temperature
    Second moment of area
    Signal-to-noise ratio (imaging)
    Single-particle spectrum
    Sound energy
    Sound energy density
    Sound exposure
    Sound intensity
    Sound power
    Sound pressure
    Specific detectivity
    Specific force
    Specific gravity
    Specific impulse

`    Specific weight
    Spectral power distribution
    Speed of sound
    Spin (physics)
    Spin angular momentum of light
    Surface power density
    System-specific impulse
`    Temperature
    Thermal conductance quantum
    Thermal conduction
    List of thermal conductivities
    Thermal conductivity
    Thermal contact conductance
    Thermal diffusivity
    Thermal effusivity
    Thermal emittance
    Thermal equilibrium
    Thermal expansion
    Thermomass theory
    Tonti diagram
    Transmission loss (duct acoustics)
`    Vapor quality
    Volume (thermodynamics)
    Volumetric flux
    Volumetric heat capacity
`    Waterproofing
    Work (physics)
`    Young's modulus

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