Question

If earth shrinks then the duration of day:

• A. increases
• B. decreases
• C. remains same
• D. first increases then decreases to inital value

Answer 1

The correct option is B decreases

Angular momentum is conserved as there is no external torque.
$\therefore L_1=L_2$
$I_1{\omega }_1=I_2{\omega }_2$
$T=\frac{2\pi }{\omega .}$
$\therefore \frac{I_1}{T_1}=\frac{I_2}{T_2}$
$\therefore$ On shrinking the earth the moment of inertia will decrease,
$\therefore$ Time duration of day will decrease as $I\propto T$