Hi first post here , I am writing an essay on the physics of the basketball shot and I'm stuck on the backboard collision. As I understand it: Starting with no spin on the basketball it follows a trajectory path until it reaches the backboard and collides with it. During this collision the basketball slides down the backboard a small distance and some of the linear velocity is changed into angular velocity. I've searched all over but I can't find out how to calculate how far it will slide. from this site http://archive.ncsa.uiuc.edu/Classes/MATH198/townsend/math.html I have the equations http://nickhv.com/img/equations.bmp [Broken] To tell me the final linear and angular velocities but I don't know how long the ball is in contact with the backboard. I know that COR = V2(second object) - V2(first object) / V1(first object) - V1(second object) So if I assume the backboard is immovable and doesn’t absorb any energy, V2(first object) = COR * V1(first object) Which leaves me with: d / t = COR * V1(first object) If I can find out the distance I can work out the time and substitute that into the original above equations for linear and angular velocity after impact. Or if there is another way to calculate the time the basketball spends in contact with the backboard I would use that. Thanks for your time.