30 Most Useful Physics Formulas

Newton's Second Law

F = ma

This formula relates force (F), mass (m), and acceleration (a). It's used to calculate the force needed to accelerate an object of a given mass.

Kinetic Energy

KE = 0.5mv²

Kinetic energy is the energy of motion. Use this formula to calculate the energy a moving object has, based on its mass and velocity.

Potential Energy

PE = mgh

Gravitational potential energy depends on an object's mass (m), gravitational acceleration (g), and height (h). Use it to determine stored energy due to elevation.

Ohm's Law

V = IR

This formula connects voltage (V), current (I), and resistance (R). It's essential in electrical circuit calculations.

Work

W = Fd

Work is calculated by multiplying force (F) and displacement (d). It represents the energy transferred when a force moves an object.

Power

P = W/t

Power measures the rate of doing work. Use this formula to calculate how quickly work (W) is done over time (t).

Hooke's Law

F = -kx

This describes the force (F) exerted by a spring. It's proportional to the displacement (x) and spring constant (k).

Momentum

p = mv

Momentum is the product of mass and velocity. It’s used in analyzing collisions and motion conservation.

Impulse

J = Ft

Impulse is the product of force and time. It represents a change in momentum caused by a force over a duration.

Centripetal Force

Fc = mv²/r

This is the force keeping an object moving in a circle. It depends on mass (m), velocity (v), and radius (r).

Gravitational Force

F = G(m1m2)/r²

Newton’s law of gravitation shows how two masses (m1, m2) attract each other with a force inversely proportional to the square of the distance between them.

Acceleration

a = (v - u)/t

This equation finds acceleration from the change in velocity (v - u) over time (t).

Velocity

v = d/t

Velocity is the rate of change of displacement over time. Use this to calculate speed with direction.

Density

ρ = m/V

Density is mass per unit volume. Useful for identifying substances or solving buoyancy problems.

Pressure

P = F/A

Pressure is the force (F) applied per unit area (A). Important in fluids and mechanical systems.

Wave Speed

v = fλ

Wave speed is found by multiplying frequency (f) by wavelength (λ). Used in sound, light, and other wave phenomena.

Period of a Wave

T = 1/f

This is the time it takes for one cycle of a wave. It is the reciprocal of frequency.

Frequency

f = 1/T

Frequency is how often a wave passes a point in a second. Reciprocal of the period.

Snell's Law

n1 sin(θ1) = n2 sin(θ2)

Describes how light bends when entering a new medium, based on refractive indices and angles of incidence/refraction.

Lens Equation

1/f = 1/do + 1/di

Relates the focal length (f) of a lens to the object distance (do) and image distance (di).

Magnification

M = hi/ho = -di/do

Describes how much larger or smaller an image is compared to the object. Involves image and object distances and heights.

Coulomb’s Law

F = k(q1q2)/r²

Describes the electrostatic force between two charges (q1, q2) separated by distance r.

Electric Field

E = F/q

Defines the electric field strength as the force (F) experienced per unit charge (q).

Electric Potential Energy

U = qV

Energy stored due to a charge (q) in an electric potential (V).

Capacitance

C = Q/V

Relates charge stored (Q) and voltage (V) across a capacitor to its capacitance (C).

Magnetic Force

F = qvB sin(θ)

Force on a moving charge in a magnetic field depends on charge, velocity, field strength, and angle.

Faraday’s Law

EMF = -dΦ/dt

Induced EMF is proportional to the rate of change of magnetic flux (Φ). Basis for electric generators.

Thermal Expansion

ΔL = αLΔT

Change in length (ΔL) of a material is proportional to its original length (L), temperature change (ΔT), and coefficient α.

Ideal Gas Law

PV = nRT

Relates pressure (P), volume (V), moles (n), gas constant (R), and temperature (T). Widely used in thermodynamics.

Efficiency

Efficiency = (Useful Energy Output / Total Energy Input) × 100%

Measures how effectively energy is converted from one form to another.