I just have a quick question. I know that at least some amount of friction is required in order for a ball to roll down an inclined plane and not just slide. My question is about the work done by friction in this situation. Is all of this energy converted to rotational kinetic energy or is there a loss of mechanical energy? Does it depend on how much friction there is between the ball and the ramp? I would appreciate any insight that you guys could give me on this situation.