1. The problem statement, all variables and given/known data A cylinder with mass 3kg slides on ice with its base surface at 5m/s and collides with an identical but stationary cylinder. The collision is elastic. After the collision, the center-masses of the cylinders move at angles 45 and 30 degrees from the starting direction, What is the rotational energy of the first cylinder? Ok so the problem I am having here is that I cannot picture the problem and that is why I am asking here as there is no sketch in the book. I do not understand how the angles are set up. 2. Relevant equations Is it any of these? : http://i.imgur.com/mXYFaDV.png I'm feeling pretty dumb, bear with me . 3. The attempt at a solution Not yet attempted.