Laws of Motion — Formula Sheet

p = mv

F = ma

F = Δp / Δt

Impulse J = F·Δt = Δp = mv − mu

F₁₂ = −F₂₁

m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂

v₂(recoil) = −(m/M)v₁

Rocket: a = −mv/M

Linear Momentum (p) = mass × velocity. It is a vector quantity with direction same as velocity.

Newton's Third Law

When two bodies interact, force exerted by body A on body B is equal in magnitude and opposite in direction to force exerted by B on A. F₁₂ = -F₂₁

Newton's Second Law

F = dp/dt = ma (for constant mass).

1 Newton = force producing 1 m/s² acceleration in 1 kg mass.

Mathematically

p_total = m₁v₁ + m₂v₂ = constant.