p = mv Formula – How to Calculate Momentum (Practice)
p = mv — Linear momentum
Linear momentum is mass times velocity: p = m v. Impulse equals the change in momentum. In collisions with no external force, total p is conserved.
Guide — how to use this formula
- 1. Convert mass to kg and velocity to m/s.
- 2. Compute p = mv, or rearrange for m or v.
- 3. Impulse: J = Δp = m(v − u).
- 4. Sticky collision: conserve total p, then divide by total mass.
Derivation
From Newton’s second law written with momentum:
- Definition:
p = mv - Force as rate of change of momentum:
F = \frac{\Delta p}{\Delta t} \Rightarrow J = F\Delta t = \Delta p
Units: kg·m/s = N·s. Convert grams and km/h before multiplying.
Examples
Example: 2 kg at 3 m/s
p = 6 kg·m/s.
Example: impulse
m = 4 kg, 0 → 8 m/s → J = 32 N·s.