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9th Class Science Work and energy Question Bank Work, Energy and Power

  • question_answer
    A body of mass m moving with velocity v suffers head on elastic collision with another body of mass 2 m at rest. The ratio of the kinetic energy off colliding body before and after collision is

    A)  9:1                          

    B)         12:1           

    C)  16 : 1                    

    D)         18 : 1         

    Correct Answer: A

    Solution :

     As discussed in question No. 45, ratio of kinetic energy of the body before and after the collision is given by,                 \[{{\left( \frac{{{u}_{1}}}{{{v}_{2}}} \right)}^{2}}={{\left( \frac{{{m}_{1}}+{{m}_{2}}}{{{m}_{1}}-{{m}_{2}}} \right)}^{2}}\] Given:   \[{{m}_{1}}=m\] and        \[{{m}_{2}}=2m\] \[\therefore \]  \[\frac{K.E{{.}_{before}}}{K.E{{.}_{after}}}={{\left( \frac{m+2m}{m-2m} \right)}^{2}}\]                 \[=9:1\]


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