1. The problem statement, all variables and given/known data A mass is placed at the top of a frictionless incline track. The bottom of the track goes into a loop. At what minimum height does the block with mass m have to be released above the ground in order to reach point b (the top of the loop). 2. Relevant equations mg(hmin)=mvb2/2 +mg2R. 3. The attempt at a solution The above formula shows that the minimum height has to be 2R because vb=0. I understand that Ugravity= mgh. But I don't understand why mv^2/2 was added on the right side. I am sitting here study my textbook and can't make sense of it.