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Question: Answered & Verified by Expert
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
PhysicsRotational MotionAIIMSAIIMS 2005
Options:
  • A decreases continuously
  • B decreases initially and increases again
  • C remains unaltered
  • D increases continuously.
Solution:
2994 Upvotes Verified Answer
The correct answer is: decreases initially and increases again
According to law of conservation of momentum,
$$
I \omega=\text { constant }
$$
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.

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