Punjab Medical Punjab - MET Solved Paper-2010

  • question_answer
    An \[\alpha -\]particle of mass \[m\] suffers one dimensional elastic collision with a nucleus of unknown mass. After the collision the \[\alpha -\]particle is scattered directly backwards losing\[75%\]of its kinetic energy. Then the mass of the nucleus is

    A) \[m\]                                    

    B) \[2m\]

    C) \[3m\]                                 

    D) \[\frac{3}{2}m\]

    Correct Answer: C

    Solution :

    \[\frac{1}{2}{{m}_{1}}u_{1}^{2}-\frac{1}{2}{{m}_{1}}v_{1}^{2}=\frac{75}{100}\times \frac{1}{2}{{m}_{1}}u_{1}^{2}\] \[\Rightarrow \]               \[t=\frac{s}{u}=\frac{50}{500}=0.1s\] \[\Rightarrow \]               \[{{v}_{1}}=\frac{1}{2}{{u}_{1}}\]                                              ? (i) Now      \[{{v}_{1}}=\frac{({{m}_{2}}-{{m}_{1}}){{u}_{1}}}{({{m}_{1}}+{{m}_{2}})}\]                            ? (ii) Thus,     \[\frac{1}{2}{{u}_{1}}=\frac{({{m}_{2}}-{{m}_{1}}){{u}_{1}}}{({{m}_{1}}+{{m}_{2}})}\] \[\Rightarrow \]               \[{{m}_{2}}=3{{m}_{1}}=3m\]


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