A cylindrical container contains some ice and the container is rotating with constant angular velocity ω0 about its own geometrical axis. Now heat is supplied to the cylinder and the ice is completely melted. Then angular velocity of the container becomes ω. Then

Due to the action of centrifugal force, water moves away from the axis of rotation, its free surface takes the form of paraboloid. As a result moment of inertia of the system increases. Since external torque is zero, its angular momentum (L) remains constant. ∴ Iω=I0ω0=L⇒ω=I0Iω0⇒ω<ω0