How to "bounce back" in "bounce ball" equations?
Or "reverse the trajectory shape" after a hit?
http://reactorlab.net/resources-folder/matlab/pdf-link-folder/bouncing_ball_equations.pdf
I don't see whether they do it in the paper.
By looking the plots one'd guess that one takes the inverse function so that the shape reverses. However, I have no idea whether this is physically accurate way of doing it.