Physics 2 — Momentum & Waves

Momentum & impulse

Momentum p = m·v is "quantity of motion" — and the only way to change it is a force acting for some time: the impulse J = F·Δt. A small force for a long time equals a big force for an instant.

m_{ball} := 0.45 kg

= 0.45 kg a football

v_{kick} := 25 m/s

= 25 m / s

p_{ball} = m_{ball} \cdot v_{kick}

= 11.25 (kg m) / s momentum after the kick

t_{contact} := 0.01 s

= 0.01 s boot-on-ball time

F_{kick} = \frac{p_{ball}}{t_{contact}}

= 1125 N the average force — surprisingly large