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AIIMS AIIMS Solved Paper-2005

  • question_answer
    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 10 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

    Correct Answer: B

    Solution :

                    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 \[=\frac{1}{2}m{{v}^{2}}=\frac{KZ{{e}^{2}}}{2r}\] Hence, if \[I\] decreases, \[\omega \] increases and vice- versa. When liquid is dropped, mass increases hence I increases \[=\frac{KZe}{r}\]. So, \[\therefore \]decreases, but as soon as the liquid starts falling \[=\text{ }potential\text{ }\times \text{ }charge\] increases again.


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