Question

A solid disc has a mass of 10kg and radius 1m. Find its radius of gyration.

(a) 1.414m

(b) 0.707m

(c) 1m

(d) 1.732

I got this question during an interview.

My query is from Moment of Inertia in section System of Particles and Rotational Motion of Physics – Class 11

Answer 1

The correct option is (b) 0.707m

To explain I would say: Moment of inertia of disc = MR^2/2 = 10*1/2 = 5kgm^2.

Radius of gyration ‘k’ is given by the expression: I = Mk^2

∴ k = √(I/M)

= √(5/10) = 0.707m.