Foot–Ball Collision
World Cup Physics
Watch the foot strike the ball — a closed-form impulse model from foot mass, foot speed, and the coefficient of restitution.
What to try
- Drop foot mass to its minimum and notice how exit speed barely exceeds foot speed — light legs cannot leverage the impulse.
- Set foot mass to 10 kg and foot speed to 25 m/s — a high-impulse strike approaching record territory.
- Sweep the coefficient of restitution from 0.4 to 0.7 at the same foot mass and speed — observe the linear bump in exit speed.
How this simulation works
Use the Foot Mass slider to set the effective swinging-leg mass (1–12 kg). Use the Foot Speed slider to set the speed of the foot at impact (5–30 m/s) — fast professional strikes sit near the top of the range. Use the Coefficient of Restitution slider to set how elastic the contact is (0.4 = soft cushion, 0.7 = stiff strike). Press Start to release the foot toward the stationary ball. The instant of contact triggers a closed-form impulse calculation; the ball flies off with the resulting velocity, and the readouts show its speed, the impulse delivered, and the fraction of foot kinetic energy transferred.