Hello everyone. Thanks for all the help today. I know I have asked a lot of questions. This is my last one today. A spherical billard ball is sliding with a speed v_o. It has a radius R, mass M, and there is a friction coefficient mu. Determine the distance the ball travels before it begins to roll smoothly on the surface. The correct answer is supposed to be 12v_o^2/(49*mu*g). I know that the kinetic energy K = (1/2)MV_cm^2 (1 + B) K = (1/2)MV_cm^2 ( 1 + 2/5) - mu*Mg*x K = (1/2)Mv_cm^2 ( 7/5) -mu*Mg*x K = (7/10)Mv_cm^2 -mu*Mg*x x = (7/10)Mv_cm^2 /(mu*mg) However, this is not the right answer. Where did I go wrong? Is it possible to solve this with energy concept? I don't know how to do it with Newton's Law. I don't know how to get velocity out of the problem.