If earth shrink (without change in mass) to half it's present size. Length of the day would become `6` hours.
As size of earth changes its moment of inertia changes.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are reason are true but reason is not the correct explanation of assertion.
C. If assertion is true but reason is false
D. If both assertion and reason are false.

Answer

A

Explanation

(a) When earth shrinks its angular momentum remains constant i.e.,
`L = I omega = (2)/(5) mR^2 xx (2 pi)/(T) = constant`
`T prop I prop R^2` it means if size of earth changes then its moment of inertia changes
If radius is half so time period will become `T//4`/ hence `24//4 = 6 Hr`.