NEET Physics Rotational Motion NEET PYQ-Rotational Motion

  • question_answer
    ABC is a right angled triangular plate of uniform thickness. The sides are such that \[AB>BC\] as shown in figure. \[{{I}_{1}},\,{{I}_{2}},\,{{I}_{3}}\] are moments of inertia about AB, BC and AC respectively. Then which of the following relations is correct?
    [AIPMT 2000]

    A) \[{{I}_{1}}={{I}_{2}}={{I}_{3}}\]

    B) \[{{I}_{2}}>{{I}_{1}}>{{I}_{3}}\]

    C) \[{{I}_{3}}<{{I}_{2}}<{{I}_{1}}\]

    D) \[{{I}_{3}}>{{I}_{1}}>{{I}_{2}}\]

    Correct Answer: B

    Solution :

    The moment of inertia of a body about an axis depends not only on the mass of the body, but also on the distribution of mass about the axis. For a given body mass is same, so it will depend only on the distribution of mass about the axis.
                The mass is farthest from axis BC, so \[{{I}_{2}}\] is maximum. Mass is nearest to axis AC, so \[{{I}_{3}}\] is minimum.
                Hence, the correct sequence will be
                            \[{{I}_{2}}>{{I}_{1}}>{{I}_{3}}\]
    Note:    In a rotational motion, moment of inertia is also known as rotational inertia.


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