Question

If radius of the earth is reduced, then ___________

(a) Time duration is reduced

(b) Earth rotates slower

(c) Time period of earth decreases

(d) Duration of day increases

The question was asked in unit test.

This intriguing question comes from Orbital Velocity topic in section Kinetic Theory of Gases of Engineering Physics I

Answer 1

Correct option is (c) Time period of earth decreases

Explanation: I=2/5 MR^2

When R decreases, the moment of inertia decreases.

But Iω=consatnt

ω=2π/T increases

Hence the period of rotation T decreases.