A small sphere `D` of mass and radius rols without slipping inside a large fixed hemispherical radius `R( gt gt r)` as shown in figure. If the sphere starts from rest at the top point of the hemisphere normal force exerted by the small sphere on the hemisphere when its is at the bottom `B` of the hemisphere.
.

Options

A. `(10 mg)/(7)`
B. `(9 mg)/(7)`
C. `(17 mg)/(7)`
D. `(3 mg)/(7)`

Answer

C

Explanation

( c) Velocity on reaching the bottom :
`mg(R - r) = (7)/(10) mv^2`
`rArr v^2 = (10)/(7) g(R - r)`
`N - mg = (mv^2)/(R - r) rArr N = (17)/(7) mg`.
.