Manipal Engineering Manipal Engineering Solved Paper-2015

  • question_answer
    A neutron moving with a speed v makes a head on collision with a hydrogen atom in ground state kept at rest. The minimum kinetic energy of neutron for which inelastic collision will take place is

    A) 10.2eV                 

    B) 20.4eV

    C) 12.1eV                 

    D) 16.8eV

    Correct Answer: B

    Solution :

    Let v = speed of neutron before collision \[\frac{1}{\sqrt{3}}\frac{\tau }{Bi}\]speed of neutron after collision \[{{m}_{1}}\]speed of hydrogen atom after collision and \[{{m}_{2}}\] energy of the excitation From the conservation of linear momentum, \[{{m}_{1}}\]                                                      ...(i) From the conservation of energy, \[{{m}_{2}}\]                      ...(ii) from Eq. (i),\[{{m}_{1}}\] From Eq. (ii),\[d\sqrt{\frac{{{m}_{1}}}{{{m}_{1}}+{{m}_{2}}}}\] \[d\sqrt{\frac{{{m}_{2}}}{{{m}_{1}}+{{m}_{2}}}}\]\[d\sqrt{\frac{2{{m}_{2}}}{{{m}_{1}}+{{m}_{2}}}}\] \[d\sqrt{\frac{2{{m}_{1}}}{{{m}_{1}}+{{m}_{2}}}}\]\[=20m{{s}^{-1}}\] \[(\text{take}\,g=10\text{ }m{{s}^{-}}^{2})\] As,\[I={{I}_{0}}\sin \omega t,\]must be real\[{{I}_{0}}=10\]\[\omega =100\pi \,\text{rad/s}\] or\[\pi \] The maximum energy that can be absorbed by hydrogen atom in ground state to go into excited state is 10.2 eV. Therefore, 'the minimum kinetic energy required is \[\pi \]


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