1. The problem statement, all variables and given/known data http://img518.imageshack.us/img518/7105/76py8.gif [Broken] 2. Relevant equations 3. The attempt at a solution I don't want a solution, just guidelines.. I don't really know how to approach it. I was thinking about an equation of conservation of momentum which will give me 2 equations (x, y) and conservation of energy (because of the ellastic collision) which will give me another equation. All in all - 3 equations, but I have 4 variables: alpha, v0, and the ball and object's speeds after the collision. What am I missing? Thank you.