Question

A circular disc of radius `R` and thickness `R//6` has moment of inertia `I` about an axis passing through its centre and perpendicular to its plane. It is melted and recast into a solid sphere. The `M.I` of the sphere about its diameter as axis of rotation is
A. `I`
B. `2I//3`
C. `I//5`
D. `I//10`

Answer 1

Correct Answer - C
`I=1/12 piR^(5)rho`, volume of disc=volume of sphere `rArr` radius of sphere `(R^(1))=R/2`