Contact animation
Foot
Ball
Compression
Ball exit speed
–
m/s
Exit speed ratio
–
vball / vfoot,in
Contact duration
–
ms
Peak force
–
N
Maximum compression
–
mm
Impulse to ball
–
N·s
Contact force over time
Foot and ball velocity
Ball compression
Kinetic and stored elastic energy
How to read the model
At the beginning, the foot is faster than the ball, so compression increases. At maximum compression, the relative velocity is approximately zero: the foot and ball momentarily move at the same speed. The compressed ball then re-expands. During that restitution phase, the foot slows while the lighter ball continues accelerating. Separation occurs when compression returns to zero and the ball is moving away faster than the foot.
This is a pedagogical one-dimensional model. Real kicks also involve foot rotation, changing contact geometry,
ball shell deformation, air pressure, friction, spin, and time-varying joint mechanics.