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NEET NEET SOLVED PAPER 2017

  • question_answer
    Two discs of same moment of inertia rotating about their regular axis passing through centre and perpendicular to the plane of disc with angular velocities \[{{\omega }_{1}}\] and\[{{\omega }_{2}}.\]They are brought into contact face to face coinciding the axis of rotation. The expression for loss of energy during this process is          

    A) \[\frac{l}{8}{{({{\omega }_{1}}-{{\omega }_{2}})}^{2}}\]                

    B)  \[\frac{1}{2}l{{({{\omega }_{1}}+{{\omega }_{2}})}^{2}}\]

    C)  \[\frac{1}{4}l{{({{\omega }_{1}}-{{\omega }_{2}})}^{2}}\]                             

    D) \[l{{({{\omega }_{1}}-{{\omega }_{2}})}^{2}}\]

    Correct Answer: C

    Solution :

                     \[\Delta KE=\frac{1}{2}\frac{{{l}_{1}}{{l}_{2}}}{{{l}_{1}}+{{l}_{2}}}{{({{\omega }_{1}}-{{\omega }_{2}})}^{2}}\]                 \[=\frac{1}{2}\frac{{{l}^{2}}}{(2l)}{{({{\omega }_{1}}-{{\omega }_{2}})}^{2}}\] \[=\frac{1}{4}l{{({{\omega }_{1}}-{{\omega }_{2}})}^{2}}\]


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