HeightEnergy
THE PHYSICS
The floor can give energy back.
A collision depends on relative velocity. When the platform rises into the ball, the impact can return more upward speed than a stationary floor could. Friction also exchanges sideways momentum and creates spin.
vrel, after = −e vrel, beforenormal collision response
The coefficient e determines how much normal relative speed survives a collision. At e = 1 the ideal collision is elastic.
Tangential impulse reduces sliding and changes both horizontal velocity and the ball’s angular velocity.
A periodically moving platform can produce stable rhythms, resonance or sensitive, irregular bouncing.