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# Physics Symbols

## What is the Importance of Physics Symbols?

Last updated date: 26th Mar 2023
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In physics, there are a large number of physical quantities we include while performing calculations. To make it more convenient for users and easier to use and remember, we often use notations/symbols to represent these physical quantities. These notations/symbols we use to represent physical quantities when solving problems related to them or for other purposes are symbols.

In physics, we symbolise everything with an English/Greek alphabet, such as for the speed of light, wavelength, velocity, and so on.

Let us assume that a lady drives her car at a speed of 30 kmph and reaches her hometown in 2 hrs and if she drives at 50 kmph, she reaches in 1.5 hr. So, if we have to represent these units as symbols, how can we do that?

In this article,  you will find the most popular physics symbols and also those we commonly use in physics with their names, the type of quantities along with their respective units in tabular format.

### Examples of Physical Symbols

Also, the symbols used for physical quantities are vastly different. Sometimes, the symbol may be the first letter of the physical quantities they represent, like ‘d’, which stands for distance. Other times, they may be completely unrelated to the name of the physical quantities, such as c symbolises the speed of light. They may also be in the form of Greek characters, like λ, which stands for wavelength.

Below is an elaborated list of the most commonly used list of symbols in physics with their SI units. Please note that a particular symbol might relate to more than one quantity.

### Symbols for Physical Quantities Related to Space and Time

 Symbols Quantity/ Coefficients S.I. Unit Physical Quantity (Scalar/Vector) r Radius, the radius of curvature Metre Functions as both scalar and vector s Displacement Metre Vector d Distance Metre Scalar θ Angular displacement, Radian Vector φ The rotational angle Radian A uniquely-defined magnitude and direction, but is not a vector quantity.(Does Not obey commutative law) x, y, z Cartesian Coordinates Unitless Scalar î, ĵ, k̂ Cartesian unit vectors Unitless Vector r, θ, φ Spherical coordinates Metre/Radian Vector r̂, θ̂, φ̂ Spherical vectors Unitless Vector r, θ, z Cylindrical coordinates Metre/Radian Scalar r̂, θ̂, ẑ Cylindrical vectors Unitless Vector n̂ Normal vector Unitless Vector t̂ Tangential unit vector Unitless Vector h Height, Depth Metre Scalar ℓ, L Length Metre Scalar t Time Second Scalar D (= 2 r) Diameter Metre Scalar C Circumference Metre Scalar A Area Square Metre Functions as both scalar and vector (like Area vector in a magnetic flux formula) V Volume Cubic Metre (m3) Scalar τ Time Constant Second (s) Scalar T Periodic time Second (s) Scalar f Frequency 1/second or (1/s) Scalar ω Angular frequency Rad/s Scalar

Below are some symbols that are used frequently in physics with their names, the type of quantities and their respective SI units in tabular format.

### Physics Symbols Related to Mechanics

 Symbols Quantity/ Coefficients S.I. Unit Physical Quantity (Scalar/Vector) v Velocity, speed metre/second (m/s) Speed = ScalarVelocity = vector a Acceleration metre/square second (m/s2) Vector g Acceleration due to gravity metre/square second Vector ac Centripetal/Centrifugal acceleration metre/square second Vector m Mass Kilogram (kg) Scalar F Force Newton (N) Vector W/Fg Force due to gravity/Weight Newton Vector Fg/ N Normal force N Vector Ff Force of friction N Vector µ Coefficient of friction Unitless Scalar p Momentum Kg.m/s Vector J Impulse N/s Vector E Energy Joule  (J) Scalar K Kinetic energy J Scalar U Potential Energy J Scalar Vg Gravitational potential J/kg Scalar η Efficiency Unitless Scalar P Power Watt Scalar α Rotational acceleration Radian per second squared (Rad/s2) Vector ω Rotational velocity Rad/s Vector τ Torque N/m Vector L Angular momentum Kilogram meter squared per secondKg.m2/s Vector ρ DensityVolume Mass density Kilogram per cubic meter Scalar I Moment of inertia Kg.m2 Scalar

### Physical Symbols Related to Fluid Mechanics

 Symbols Quantity/ Coefficients S.I. Unit Physical Quantity (Scalar/Vector) λ Linear mass density kg/m Scalar σ Area mass density Kilogram per square meter (kg/m2) Scalar FB, B Buoyancy N Vector qm Mass flow rate kg/s Scalar qV Volume flow rate m3/s Scalar FD, R Drag or air resistance N Vector CD Drag Coefficient Unitless Scalar η Viscosity Pascal-second Scalar v Kinematic Viscosity m2/s Scalar σ Area mass density kg/m2 Scalar Re Reynolds number Unitless Scalar Fr Froude number Unitless Scalar Ma Mach number Unitless Scalar

### Symbols Related to Solid Mechanics

 Symbols Quantity/ Coefficients S.I. Unit Physical Quantity (Scalar/Vector) P Pressure PascalOrN/m2 Scalar σ Stress Pascal Scalar τ Shear stress Pascal Scalar k Spring constant N/m Scalar E Young’s modulus of elasticity Pascal Scalar G Shear modulus of rigidity Pascal Scalar ε Linear strain Unitless Scalar γ Shear strain Unitless Scalar θ Volume strain Unitless Scalar S Surface Tension N/m Scalar K Bulk modulus of compression Pascal Scalar

### Physical Quantities Related to Thermal Physics

 Symbols Quantity/ Coefficients S.I. Unit Physical Quantity (Scalar/Vector) k Thermal conductivity W/m.K Scalar P Heat flow rate Watt Scalar N Number of particles Unitless Scalar n Amount of substance Mole Scalar L Latent heat/specific latent heat J/kg Scalar c Specific heat capacity J/kg. K Scalar Q Heat J Scalar B Volume expansivity, coefficient of volume thermal expansion 1/K (inverse Kelvin) Scalar α Linear expansivity, coefficient of thermal expansion 1/K (inverse Kelvin) Scalar T Temperature Kelvin Scalar

### Physical Symbol Related to Wave and Optics

 Symbol Quantity/Coefficients S.I Unit Physical Quantity (Scalar/Vector) M Magnification Untiless Scalar f Focal length Metre Scalar n Index of refraction Unitless Scalar L Level Decibel (dB), decineper Scalar I Intensity W/m2 Scalar v, c Wave speed m/s Scalar λ Wavelength Metre (m) Scalar P Power of a lens Dioptre (D) Scalar

### Physics Symbols Related to Electricity and Magnetism

 Symbol Quantity/Coefficients S.I Unit Physical Quantity (Scalar/Vector) S Poynting vector, intensity W/m2 Vector η Energy density J/m3 Scalar n Turns per unit length 1/m Scalar N Number of turns Unitless Scalar φB Magnetic flux Weber Vector B Magnetic field Tesla Vector FB Magnetic force N Vector σ Conductivity Siemens/m (S/m) Scalar G Conductance Siemens Scalar ρ Resistivity Ohm-m Scalar R, r Electric resistance/internal resistance Ohm Scalar I Electric current Ampere (A) Scalar ϵ Dielectric constant Unitless Scalar ℰ Electromotive Force Volt (V) Scalar C Capacitance Farad (F) Scalar V Voltage, electric potential V Scalar UE Electric potential energy J Scalar φE Electric flux Newton meter squared per coulomb (N/m2.C) Vector E Electric field N/C or V/m Vector FE Electrostatic force N Vector λ Linear charge density kg/m Scalar σ Area charge density kg/m2 Scalar ρ Volume charge density kg/m3 Scalar q, Q Electric charge Coulomb (C) Scalar

### Symbols Used in Modern Physics

 Symbol Quantity/Coefficients S.I Unit Physical Quantity (Scalar/Vector) D Dose/ dose absorbed Gray (Gy) Scalar t1⁄2 Half-life Second Vector ψ(r,t), ψ(r)φ(t) Wave function Unitless Scalar W Work function J Scalar H Effective Dose Sievert Scalar Γ Lorentz factor/Lorentz gamma Unitless Scalar

From the above text on physics symbols, we understand that in Physics, we use various symbols or notations to denote different quantities. The denotations make the representation of the quantities easier.

It was also interesting to see that some physics symbols were very relatable (like “d” for distance) while some were unrelatable (like “c” for the speed of light or “λ” for wavelength). Also, we noticed that a particular symbol was related to more than one quantity.