This is driving me crazy. I need to make sure I'm reading my physics homework correctly. Alright, a uniform, solid ball is pushed with initial velocity V(0) so that it slides. As the ball moves, kenetic friction between the ball and the surface it is traveling on causes the ball to rotate untill it reaches some constant speed V(f). I need to find V(f) in terms of V(0) and the question walks through different ways to find it. Part B: Show that the net torque on the ball is zero about any point O along the ball's path on the surface. What does this imply about the Ball's total angular momentum about O? This question is attempting to show that the torque about any point on teh surface of the ball is 0, correct? Being tha the torque is 0 about such points, the angular momentum about such points would be constant. Part C: Write expressions for the ball's initial and final angular momentum about point O. Equate these to find the ball's final linear speed V(f). Does yoru result depend on the ball's mass M and/or radius R? If point O is on the surface of the ball, then the torque about O is 0 as we established in Part B. How the hell can you have a initial and final angular momentum about O if the torque about O is 0?!?!?! I must be misreading this part and its driving me crazy.