Question

How is the answer d??

Answer 1

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