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A horizontal platform is rotating with uniform angular velcity 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 continouslyB. remains unlteredC. decreases initially and increases againD. increases continuously |
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Answer» Correct Answer - C ( c) From law of conservation of angular momentum if no external torque is acting upon a body rotating about an axis, then the angular momentum of the body remains constant that is `J = I omega = constant` Hence, if decreases, `omega` increases and vice-versa. When liquid is dropped, mass increase hence `I` increases `(I = mr^2)` So, `omega` decreases, but as soon as the liquid starts falling `omega` increases again. |
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