A body is allowed to slide down a frictionless track from rest position at its top under gravity. The track ends in a circular loop of diameter `D`. Then, the minimum height of the inclined track (in terms of `D`) so that it may complete successfully the loop is

Options

A. `7D//4`
B. `9D//4`
C. `5D//4`
D. `3D//4`

Answer

C

Explanation

Loss `P.E` = gain in `K.E , mgh = (1)/(2) m[sqrt(5 gr)]^(2)`.