Question

A horizontal platform is rotating with uniform angular velocity around the vertical axis passing through its centre. At some instant of time, a viscous fluid of mass m is dropped at the centre and is allowed to spread out and finally fall. The angular velocity during this period

(a) decreases continuously

(b) decreases initially and increases again

(c) remains unaltered

(d) increases continuously.

Answer 1

Correct option (b) decreases initially and increases again

Explanation :

According to law of conservation of angular momentum, Iω = constant.

When viscous fluid of mass m is dropped and start spreading out then its moment of inertia increases and angular velocity decreases. But when it start falling then its moment of inertia again starts decreasing and angular velocity increases.