NEET AIPMT SOLVED PAPER MAINS 2010

  • question_answer
      From a circular disc of radius R and mass 9 M, a small disc of mass M and radius \[\frac{R}{3}\]is removed concentrically. The moment of inertia of the  remaining disc about an axis perpendicular to  the plane of the disc and passing through its centre is                        

    A) \[\frac{40}{9}M{{R}^{2}}\]          

    B) \[M{{R}^{2}}\]  

    C) \[4M{{R}^{2}}\]

    D) \[\frac{4}{9}M{{R}^{2}}\]

    Correct Answer: A

    Solution :

    The moment of inertia of the remaining disc about an axis perpendicular to the plane of the disc and passing through its centre \[I={{I}_{1}}-{{I}_{2}}\] \[=\frac{9M{{R}^{2}}}{2}-\frac{M{{R}^{2}}}{18}\] \[=\frac{81M{{R}^{2}}-M{{R}^{2}}}{18}\] \[=\frac{40M{{R}^{2}}}{9}\]


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