Question

An ice block is in a cylindrical container (as shown in figure) which is rotating about vertical axis passing through its center. When the ice melts completely, the angular velocity of the system:

• A. increases
• B. decreases
• C. remains same
• D. will not change dramatically

Answer 1

The correct option is B decreases

No external torque,
$\therefore$ Angular momentum is constant.
$L=$constant,
$I\omega =$constant
$I\propto \frac{1}{\omega .}$
When ice melts, the water will flow towards the edge away from the axis of rotation due which moment of inertia of the system get increased, which results in the decrease of the angular velocity of the system.