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9th Class Science Work and energy Question Bank Work Power and Energy IIT JEE Objective Problems

  • question_answer
    Two bodies of masses 2 kg and 3, kg have same momenta. K.E. of 3 kg mass is 10 J. then K.E. of 2 kg mass is

    A)  50 J                                       

    B)  15 J

    C)  25 J                                       

    D)  20 J

    Correct Answer: B

    Solution :

     
    Body 1 Body 2
    Mass \[({{m}_{1}})=2\,\,kg\] Mass \[({{m}_{2}})=3\,\,kg\]
    Momentum\[({{p}_{1}})=p\] Momentum\[({{p}_{2}})=p\]
    \[K.E{{.}_{1}}=?\] \[K.E{{.}_{2}}=10J\]
    We know that, \[K.E.=\frac{{{p}^{2}}}{2m}\] \[\Rightarrow K.E.\,\alpha \frac{1}{m}\]                                            (\[\because \] ?p? is same) \[\therefore \,\,\frac{K{{E}_{1}}}{K{{E}_{2}}}=\frac{{{m}_{2}}}{{{m}_{1}}}\Rightarrow \frac{K{{E}_{1}}}{10}=\frac{3}{2}\Rightarrow K.E{{.}_{1}}=15\,J\]


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