NEET Sample Paper NEET Sample Test Paper-70

  • question_answer
    Four thin rods of the same mass M and the same length l form a square as shown in the figure. Moment of inertia of this system about an axis through centre O and perpendicular to its plane is

    A) \[\frac{4}{3}\,M{{l}^{2}}\]

    B) \[\frac{M{{l}^{2}}}{3}\,\]

    C) \[\frac{M{{l}^{2}}}{6}\,\]              

    D) \[\frac{2}{3}\,M{{l}^{2}}\]

    Correct Answer: A

    Solution :

    Moment of inertia of rod AB about point \[P=\frac{1}{12}\,M{{l}^{2}}\] MI of rod AB about point \[O=\frac{M{{l}^{2}}}{12}+M{{\left( \frac{1}{2} \right)}^{2}}\] \[=\,\,\frac{1}{3}\,M{{l}^{2}}\]      [by the theorem of parallel axis] and the system consists of 4 rods of similar type so by the symmetry /system \[{{I}_{system}}=\,\,\frac{4}{3}\,\,M{{l}^{2}}\]                      


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