KVPY Sample Paper KVPY Stream-SX Model Paper-27

  • question_answer
    A ball\[A\], moving with kinetic energy\[k\], makes a head on elastic collision with a stationary ball with mass n times that of\[A\]. The maximum potential energy stored in the system during the collision is

    A) \[k/n\]   

    B) \[\frac{\left( n-1 \right)k}{n}\]

    C) \[\frac{\left( n+1 \right)k}{n}\]

    D) \[\frac{nk}{\left( n+1 \right)}\]

    Correct Answer: D

    Solution :

    Given, \[k=\frac{1}{2}m{{v}^{2}}\]
    If \[v'\] is the velocity of the balls during collision, then
    \[mv+0=(m+nm){v}'\,\,\,\,\,\,;\,\,\,\,\,\,\,\,v'=\left( \frac{v}{n+1} \right)\]
    The maximum potential energy stored during collision,
    \[=\frac{1}{2}m{{v}^{2}}-\frac{1}{2}\left( m+nm \right)v{{'}^{2}}\]
    \[=\frac{1}{2}m{{v}^{2}}-\frac{1}{2}\left( n+1 \right)\frac{m{{v}^{2}}}{{{\left( n+1 \right)}^{2}}}\]
    \[=k-\frac{k}{n+1}=\frac{nk}{n+1}\]


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