1. The problem statement, all variables and given/known data A hoop is launched so that it slides with backspin across the floor. Due to friction on the floor, the hoop eventually reverses direction. A little after that, it stops slipping and rolls back to the point where it was launched. If the initial speed of the hoop was v and its initial angular velocity was omega, what is its speed as it rolls back? 2. Relevant equations L = Iw + mvr Iw = Iw for conservation 3. The attempt at a solution L = Iw - mvr (I thought "-" because of friction). I need to find the total angular momentum of the hoop with respect to a stationary point on the floor, but I am not sure how to do this mathematically. The angular momentum with respect to the hoop rolling back has to equal the angular momentum with friction making it slip away. Is the point of slip/roll significant?