Ok so a ball starts moving to the left while the rotation is clockwise, hence the backspin. On this surface there is friction. So clearly as the ball moves to the left, there is Kinetic friction to the right slowing down the Vcm and the spin as well. So assuming that the initial backspin is large enough such that that eventually the Vcm becomes momentarily 0 while the ball is still spinning clockwise. At this point, what will happen? I've heard two things. 1: the kinetic friction pointing to the right will reverse the Vcm and increase it until it starts rolling without slipping. 2: A the moment the Vcm is 0, the ball immediately starts pure roll to the right and returns to where it started. Which one is more plausible? I'm thinking #1 is because the backspin will cause friction to the right even though the Vcm is 0. Hence causing a short time interval where there is still slipping. But #2 is somewhat plausible as well. If the material of the friction is low, maybe the kinetic friction will not exist at that instant when Vcm is 0, because the backspinight be weak to cause friction.