Answer:
To keep from falling at the top;
M V^2 / R = M g
This can be rewritten
1/2 M V^2 = M g R /2
2 M g R = 1/2 M V^2 difference in KE between top and bottom
2 M g R + M g R / 2 = 5/2 M g R
Adding the minimum KE at the top to the KE gained when the potential energy of 2 M g R is converted to KE
