NEET Physics Rotational Motion NEET PYQ-Rotational Motion

  • 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: [AIPMT (S) 2006]

    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 the disc and R its radius. 
                According to theorem of parallel axis, ML 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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