RAJASTHAN PMT Rajasthan - PMT Solved Paper-2005

  • question_answer
    Out of the given bodies (of same mass) for which the moment of inertia will be maximum about the axis passing through its centre of gravity and perpendicular to its plane?

    A)  Disc of radius\[a\]

    B)  Ring of radius\[a\]

    C)  Square lamina of side\[2a\]

    D)  Pour rods of length \[2a\] making a square

    Correct Answer: D

    Solution :

    For square of side, \[I=\frac{1}{2}m{{a}^{2}}\]                   For ring, \[I=m{{a}^{2}}\]                  For square of side \[2a\]     \[=\frac{M}{12}{{[2a]}^{2}}+{{(2a)}^{2}}]=\frac{2}{3}M{{a}^{2}}\] For square of rod of length \[2a\] \[I=4\left[ M\frac{{{(2a)}^{2}}}{12}+M{{a}^{2}} \right]=\frac{16}{3}M{{a}^{2}}\] Hence, moment of inertia is maximum for square of four rods.


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