Hi all, I've begun learning how to use Unity Physics engine by creating a simple example which is the "Ideal Free Fall" of a ball. I've prepared a surface and a ball which falls from the sky. The ball has the rigidbody component inside itself while the surface has only a box collider. Both the ball and the surface have a simple Physic Material which has this setup: Friction (Dynamic and Static): 0 Bounciness: 1 Friction combine: Minimum Bounce combine: Minimum Friction Direction 2 (and others): all set to 0. The ball has no angular drag and no drag at all. The surface is not moving. While I start the simulation the ball begins rebounding as expected with the exception that for every rebound it makes the ball acquires some energy and goes higher than the starting point. I'm a bit confused... is there any parameter I did not consider? Mass of the ball is 1 and the interacting surface has no rigidbody component. Thank you in advance for your answers.