1. The problem statement, all variables and given/known data A block of mass m starts from rest from a height h and slides down along a loop with radius r. What should the initial height h be so that m pushes against the top of the track with a force equal to its weight? (ignore friction) 2. Relevant equations U = mgh K = 1/2 mv^2 F = mg = mv^2/r 3. The attempt at a solution So the force should be equal to its weight (mg) which I set equal to mv^2/r. So at rest, m has a potential energy of mgh. At the bottom on the incline before entering the loop, m has a kinetic energy of 1/2 mv^2. Since there is no external forces, U = K. Solving the force equation, I got v^2 = gr. The height h = v^2/2g. My answer ends up being h = r/2, but I have the correct answer, 3r. What am I missing here?