Question

The moment of inertia of a solid sphere is 10kgm^2. What will be the moment of inertia of a very thin spherical shell of the same mass and radius as that of the solid sphere?

(a) 16.67kgm^2

(b) 6kgm^2

(c) 10kgm^2

(d) 20kgm^2

The question was asked at a job interview.

My question is based upon Moment of Inertia in section System of Particles and Rotational Motion of Physics – Class 11

Answer 1

Correct option is (a) 16.67kgm^2

Easiest explanation: Moment of inertia of solid sphere ‘I1’ = 2/5 MR^2 = 10kgm^2.

Moment of inertia of thin spherical shell ‘I2’= 2/3 MR^2.

∴  I2 = 5/3I1

= 5/3 * 10 = 16.67kgm^2.