I do not know if my problem is advanced, but in any case I place it here Well this it : A ball bounces in the stairs of a staircase. Let l=-(Vfk/Vik) where Vfk the velocity just before the colision with a stair and Vik the velocity just after. the height and the Length of the stairs is L (the same). The ball always reaches he same height H (from the stair). The ball always travels the same distance X between two coisions with the stares. I want to find the H and Vx using L and l only (H = f (L,l), Vx = f (L,l)). Any help? The shape is not so good but I hope you understand the concept..