1. The problem statement, all variables and given/known data A 120 kg hoop rolls along a horizontal floor so that its center of mass has a speed of 0.240 m/s. How much work must be done on the hoop to stop it? 2. Relevant equations I of hoop=MR^2 3. The attempt at a solution KE=0.5*m*v^2+0.5*(mR^2)(v/R)^2 =0.5*120kg*.24^2m/s+0.5*(120kg*R^2)(.24m/s^2/R^2) =6.912 J .