Physics

Equations of motion

v = u + at, s = ut + ½at², v² = u² + 2as

Newton's second law

F = ma

SI unit: newton (N)

Momentum

p = mv

Work

W = F × s × cos θ

Unit: joule (J)

Kinetic & potential energy

KE = ½mv², PE = mgh

Power

P = W / t

1 hp = 746 W

Gravitation

F = G m₁m₂ / r²

g ≈ 9.8 m/s² on Earth

Pressure

P = F / A, liquid: P = hρg

Unit: pascal (Pa)

Density

ρ = m / V

Wave speed

v = f × λ

Ohm's law

V = IR

Resistors

Series: R = R₁ + R₂, Parallel: 1/R = 1/R₁ + 1/R₂

Electric power

P = VI = I²R = V²/R

1 kWh = 3.6 × 10⁶ J

Heating effect

H = I²Rt

Joule's law

Mirror & lens

Mirror: 1/f = 1/v + 1/u, Lens: 1/f = 1/v − 1/u

Magnification & power

m = h'/h, P = 1/f (f in metres)

Unit of power: dioptre (D)

Refractive index

n = c / v = sin i / sin r

Heat

Q = mcΔT

Water c = 4186 J/kg°C

Temperature scales

K = °C + 273, °F = (9/5)°C + 32

−40 °C = −40 °F

Escape velocity

vₑ = √(2gR)

≈ 11.2 km/s for Earth

Coulomb's law

F = kq₁q₂ / r²

k = 9 × 10⁹ N m²/C²

Hooke's law

F = kx

Within elastic limit

Centripetal force

F = mv²/r

Simple pendulum

T = 2π√(l/g)

Photon energy

E = hf = hc/λ

h = 6.63 × 10⁻³⁴ J s

Mass–energy

E = mc²

Buoyant force

F = ρVg

ρ, V of displaced liquid