JIPMER Jipmer Medical Solved Paper-2015

  • question_answer
    A thin circular ring of mass M and radius r is rotating about its axis with a constant angular velocity co. Two objects each of mass m are attached gently to the opposite ends of a diameter of the ring. The ring will now rotate with an angular velocity of:

    A)  \[\frac{\omega \,(M-2m)}{(M+2m)}\]  

    B)         \[\frac{\omega M}{(M+2m)}\]

    C)  \[\frac{\omega M}{(M+m)}\]   

    D)         \[\frac{\omega (M+2m)}{M}\]

    Correct Answer: B

    Solution :

    Given: Mass of ring = M; Radius of ring = r; Initial angular velocity \[({{\omega }_{1}})=\omega ;\] Mass added with the ring = 2 m and final angular velocity\[({{\omega }_{2}}).\] We know from the conservation of angular moment\[{{I}_{1}}{{\omega }_{1}}={{I}_{2}}{{\omega }_{2}}\] or \[M{{r}^{2}}\omega =(M+2m)\,{{r}^{2}}\omega \]or\[\omega =\frac{\omega M}{(M+2m)}\]


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