Q. 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
Explanation
(b) According to law of conservation of momentum
$I\omega =$ 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 falls from the platform moment of inertia decreases so angular velocity increases again
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.