Haryana PMT Haryana PMT Solved Paper-2008

  • question_answer
    The moment of inertia of a uniform circular disc of radius R and mass M about an axis touching the disc at its diameter and normal to the disc is

    A) \[M{{R}^{2}}\]                                                                   

    B)  \[\frac{2}{5}M{{R}^{2}}\]

    C)  \[\frac{3}{2}M{{R}^{2}}\]                            

    D) \[\frac{1}{2}M{{R}^{2}}\]

    Correct Answer: C

    Solution :

                    The moment of inertia about an axis passing through centre of mass of disc and , perpendicular to its plane is \[{{I}_{CM}}=\frac{1}{2}M{{R}^{2}}\]where M is the mass of disc and R its radius. According to theorem of parallel axis, moment of inertia of circular disc about an axis touching the disc at its diameter and normal to the disc is                 \[I={{I}_{CM}}+M{{R}^{2}}\]                 \[=\frac{1}{2}M{{R}^{2}}+M{{R}^{2}}\]                 \[=\frac{3}{2}M{{R}^{2}}\]


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