Chhattisgarh PMT Chhattisgarh PMT Solved Paper-2006

  • question_answer
    If the moment of inertia of a disc about an axis tangential and parallel to its surface be \[I,\] then what will be the moment of inertia about the axis tangential but perpendicular to the surface?

    A) \[\frac{6}{5}I\]                                 

    B) \[\frac{3}{4}I\]

    C) \[\frac{3}{2}I\]                                 

    D) \[\frac{5}{4}I\]

    Correct Answer: A

    Solution :

    Moment of inertia of disc about a tangent and parallel to its plane, \[I=\frac{M{{R}^{2}}}{4}+M{{R}^{2}}=\frac{5}{4}M{{R}^{2}}\]          ?..(i) Moment of inertia of disc about a tangent and perpendicular to its plane, \[=\frac{M{{R}^{2}}}{2}+M{{R}^{2}}\] \[=\frac{3}{2}M{{R}^{2}}\]                 \[\therefore \]                   \[\frac{I}{{{I}_{perpendicular}}}=\frac{\frac{5}{4}M{{R}^{2}}}{\frac{3}{2}M{{R}^{2}}}=\frac{5}{6}\]                 \[\therefore \]  \[{{I}_{perpendicualr}}=\frac{6}{5}I\]


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