BHU PMT BHU PMT Solved Paper-2003

  • question_answer
    Five particles of mass \[2\,kg\] are attached to the rim of a circular disc mass radius 0.1 m and negligible mass. Moment of inertia of the system about the axis passing through the center of the disc and perpendicular to its plane is:                                                                                                                                   [BHU M-2003]

    A)  \[1\,\,kg\,\,{{m}^{2}}\]               

    B)  \[0.1\,\,kg\,\,{{m}^{2}}\]

    C)  \[2\,\,kg\,\,{{m}^{2}}\]               

    D)  \[0.2\,\,kg\,\,{{m}^{2}}\]

    Correct Answer: B

    Solution :

                     Key Idea: Since disc is of negligible mass moment of inertia is due to particles attached to its rim. The moment of inertia of a rigid body about a given axis is the sum of the products of the masses of its particles by the square of their respective distance from the axis of rotation.                 \[\therefore \]  \[I=\Sigma \,m\,{{r}^{2}}\]                                 \[I=5\times 2\times {{\left( 0.1 \right)}^{2}}=0.1\,kg\,{{m}^{2}}\]


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