JEE Main & Advanced Sample Paper JEE Main Sample Paper-7

  • question_answer
    A nucleus of mass number \[A=220\] at rest undergoes an a-decay. If the Q-value of the decay is 5.5 Me V, the kinetic energy of the a-particle is

    A)  5.0 MeV             

    B)  5.4 MeV

    C)  5.6 MeV             

    D)  6.0 MeV

    Correct Answer: B

    Solution :

    \[_{z}{{X}^{220}}\xrightarrow{\,}{{\,}_{2}}H{{e}^{4}}{{+}_{z-2}}{{Y}^{216}}+5.5\,\,meV\] \[|{{p}_{y}}|=|{{p}_{\alpha }}|\Rightarrow \,\sqrt{2{{m}_{y}}{{E}_{y}}}=\sqrt{2{{m}_{\alpha }}-{{E}_{\alpha }}}\] \[216{{E}_{y}}=4{{E}_{\alpha }}\] Also, \[{{E}_{\alpha }}+{{E}_{y}}=5.5\,\,MeV\] Solve to get K.E. of \[\alpha ={{E}_{\alpha }}=5.4\,MeV\]


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