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JEE Main & Advanced Physics Rotational Motion Question Bank Self Evaluation Test - System of Particles Rotational Motion

  • question_answer
    \[(n-1)\] equal point masses each of mass m are placed at the vertices of a regular n-polygon. The vacant vertex has a position vector a with respect to the centre of the polygon. The position vector of centre of mass is

    A) \[-\frac{1}{(n-a)}a\]

    B) \[\frac{a}{(n+1)}\]

    C) \[\frac{a}{n}\]

    D) \[\frac{n}{a+1}\]

    Correct Answer: A

    Solution :

    [a] Let the C.M. be 'b'. Then, \[\frac{(n-1)mb+ma}{mn}=0\Rightarrow b=-\frac{1}{n-1}a\]


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