AIIMS AIIMS Solved Paper-2015

  • question_answer
    A massless rod S having length 27 has equal point masses attached to its two ends as shown in figure. The rod is rotating about an axis passing through its centre and making angle \[\alpha \]with the axis. The magnitude of change of momentum of rod i.e. \[V={{v}_{0}}-{{({{\omega }^{3}}{{X}^{3}}{{e}^{{{X}^{3}}}})}^{1/3}}\] equals

    A) \[\frac{2\,{{m}^{2}}}{3}g\]

    B) \[\frac{4\,{{m}^{2}}}{3}g\]

    C) \[\frac{\,{{m}^{2}}}{\sqrt{2}}g\]

    D) \[5\Omega \]

    Correct Answer: B

    Solution :

    The radius of the circle followed by the masses is \[r=l\sin \alpha \]As, angular momentum, \[\xrightarrow{\text{ROOR (peroxide)}}\underset{Major}{\mathop{(X)}}\,+\underset{Minor}{\mathop{(Y)}}\,\]                                                 \[BrC{{H}_{2}}-C{{H}_{2}}-CH=C{{H}_{2}}\] \[{{C}_{2}}{{H}_{5}}-CHBr-C{{H}_{3}}\]   \[|L|=l\sin \theta (m\omega lsin\theta )\] On differentiating, we get \[\frac{d|L|}{dt}=m\omega {{l}^{2}}2\sin \theta \frac{d\theta }{dt}\] \[\Rightarrow \]\[\left| \frac{dL}{dt} \right|=2m{{l}^{2}}{{\omega }^{2}}\sin \theta .cos\theta \] \[=m{{l}^{2}}{{\omega }^{2}}\sin 2\theta \]


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