Punjab Medical Punjab - MET Solved Paper-2008

  • question_answer
    A sphere of mass m moving with constant velocity\[u\], collides with another stationary sphere of same mass. If e is the coefficient of restitution, the ratio of the final velocities of the first and second spheres is

    A) \[\frac{1+e}{1-e}\]                                         

    B) \[\frac{1-e}{1+e}\]

    C) \[\frac{e}{1-e}\]                                              

    D) \[\frac{1+e}{e}\]

    Correct Answer: B

    Solution :

    Let \[{{v}_{1}},\,\,{{v}_{2}}\] be the final velocities of the two spheres. Applying the law of conservation of linear momentum                 \[mu=m({{v}_{1}}+{{v}_{2}})\] or                            \[{{v}_{1}}+{{v}_{2}}=u\]                              ... (i) Again the coefficient of restitution is given by                 \[e=\frac{{{v}_{2}}-{{v}_{1}}}{u}\] or            \[{{v}_{1}}+{{v}_{2}}=u\]                                              ... (ii) Solving Eqs. (i) and (ii), we get                                 \[{{v}_{1}}=\frac{u}{2}(1-e),\,\,{{v}_{2}}=\frac{u}{2}(1+e)\] Therefore,          \[\frac{{{v}_{1}}}{{{v}_{2}}}=\left( \frac{1-e}{1+e} \right)\]


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