1. The problem statement, all variables and given/known data I am not asking you to help me solve this, so i won't put in any usefull relevant equations or attempts at a solution. The nature of my problem is more of an understanding this collision - it is more of a thinking thing to process here. The problem goes like this. Ball is rolling with some initial velocity and it collidies with the same ball (standing still at the moment). The surface is frictionless but there is a friction beetween 2 balls. The translation part of energy is conversed. Surfaces of the balls are sliding against each other while collision. The question is - what are the translational and rotational velocities of the second ball after the collision. But it is not about the question. I have a trouble understanding what is happening during the collision. Many quetions came to my mind. The surface is frictionless and but the surfaces of the balls are not. Then how the ball is even rolling? Or was it intentionally rotated with the speed ωr that was the same as translational velicity If they mean that table has static friction but not the kinetic friction my mental image of the problem is completly different. the first ball is rotating in the negative direction (clockwise) and it it tries to make the second ball rotating in the positive direction (counter clockwise). However if we assume that they mean the table has in fact static friction (if not how the ball is even rolling) then the kineticfriction would try to slow down the rotation of the second ball in negative direction (the translational energy fromthe first ball is distribuated beetween the rotational an kinetic energy of the second ball) if the rotation in negative direction is then lower than it should be the ball then would not be rolling - but in fact slipping. So the question is - it must have lower translational velocity too. And the first ball must collide back and have some translational velocity too (which makes sense in a way) but how can i know how much the ball is slowing down the rolling of the second ball, if i don t have a time of the collision and force of friction? I am sorry. I am completly lost and i know this thought process is probably wrong in so many ways and really hard to follow. How do you understand the collision? What would happen with the first and the second ball in your opinion. Thank you for any kind of information regarding this painfull problem. 2. Relevant equations No equations needed - it is a matter of thought, please read the intro if you want to report not following the template... 3. The attempt at a solution Thinking beyond imaginable. My head will explode.