Physics Formulas

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The formulas for motion, force, energy, electricity, waves and heat — searchable in either language, each with what its symbols mean

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In either language

Name or quantity

There are separate tools that calculate motion and Ohm's law — both in this category.

Motion

Average velocityv = s ⁄ t

s = displacement, t = time

Accelerationa = (v − u) ⁄ t

u = initial velocity, v = final velocity

First equation of motionv = u + at

final velocity from time

Second equation of motions = ut + ½at²

displacement from time

Third equation of motionv² = u² + 2as

velocity and displacement without time

Force and energy

Newton's second lawF = ma

m = mass, a = acceleration

WeightW = mg

g ≈ 9.8 m/s²

Momentump = mv

a conserved quantity

WorkW = F·s·cos θ

θ = angle between force and displacement

Kinetic energyEₖ = ½mv²

double the speed, four times the energy

Potential energyEₚ = mgh

h = height

PowerP = W ⁄ t

measured in watts

Circular motion and gravity

Centripetal forceF = mv² ⁄ r

r = radius

Law of gravitationF = G·m₁m₂ ⁄ r²

G = 6.67 × 10⁻¹¹

Electricity

Ohm's lawV = IR

V = voltage, I = current, R = resistance

Electrical powerP = VI = I²R = V² ⁄ R

three routes to the same figure

Resistors in seriesR = R₁ + R₂ + R₃ …

they simply add

Resistors in parallel1⁄R = 1⁄R₁ + 1⁄R₂ …

the result is smaller than the smallest of them

ChargeQ = It

measured in coulombs

Waves and light

Wave equationv = fλ

f = frequency, λ = wavelength

PeriodT = 1 ⁄ f

the inverse of frequency

Snell's lawn₁ sin θ₁ = n₂ sin θ₂

n = refractive index

Lens formula1⁄f = 1⁄v − 1⁄u

f = focal length

Heat

Heat energyQ = mcΔθ

c = specific heat capacity

Latent heatQ = mL

during a change of state, with no rise in temperature

Densityρ = m ⁄ V

V = volume

PressureP = F ⁄ A

A = area

Understanding which quantity sits where is worth more than memorising the line — and in an exam, the units are what catch you. Cancel the units through before writing the answer: a wrong formula almost always leaves them not matching.

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