Question

Calculate the moment of inertia of the earth about its diameter, taking it to be a sphere of 10^25kg and diameter 12800km.

(a) 1.64 kgm^2

(b) 16.4×10^38 kgm^2

(c) 1.64×10^38 kgm^2

(d) 0

I had been asked this question in final exam.

This question is from Centripetal Force topic in portion Kinematics of Engineering Physics I

Answer 1

Right option is (c) 1.64×10^38 kgm^2

The explanation: M = 10^25kg, R = 6400km = 6.4×10^6 m

Moment of inertia of the earth about its diameter I = 2/5 MR^2 = 2/5×10^25×(6.4×10^6)^2

I = 1.64×10^38 kgm^2.