NEET Physics NLM, Friction, Circular Motion NEET PYQ-NLM Friction Circular Motion

  • question_answer
    A circular platform is mounted on a frictionless vertical axle. Its radius \[R=2\,m\] and its moment of inertia about the axle is \[200\text{ }kg\text{ }{{m}^{2}}\]. It is initially at rest. A 50 kg man stands on the edge of the platform and begins to walk along the edge at the speed of \[1\,\,m{{s}^{-1}}\] relative to the ground. Time taken by the man to complete one revolution is                       [AIPMT (M) 2012]

    A) \[\pi \sec \]

    B) \[\frac{3\pi }{2}\sec \]

    C) \[2\pi \sec \]

    D) \[\frac{\pi }{2}\sec \]

    Correct Answer: C

    Solution :

    From conservation of angular momentum
                            \[I\omega =mvr\]
                            \[200\times \omega =50\times 2\times 1\]
                            \[\omega =\frac{1}{2}rad/s\]
                            \[v=r\omega =1m/s\]
                \[\therefore \]      \[T=\frac{2\pi r}{1-(-1)}=\frac{2\pi r}{2}=\pi r=2\pi s\]


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