1. The problem statement, all variables and given/known data part(b) and (c) 2. Relevant equations Conservation of momentum Conservation of angular momentum Conservation of mechanical energy 3. The attempt at a solution So first I thought that I could do it by just using the conservation of mechanical energy, but then I realized that since the lower part of the hoop hits the platform, the energy can't be conserved (there's energy lost): 1/2 mv^2 + 1/2 Iw^2 = mgh + Energy lost mv^2 = mgh + Energy lost I think that part (b) and (c) is very related, once we know the energy lost, we can determine the v needed, however I don't really understand how to find its value. Any suggestion ??