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

  • question_answer
    A moving body with a mass \[{{m}_{2}}\]\[{{m}_{1}}\] strike a stationary body of mass \[{{m}_{2}}\]. The masses  \[{{m}_{2}}\]and \[{{m}_{2}}\] should be in the ratio \[\frac{{{m}_{1}}}{{{m}_{2}}}\] so as to decrease the velocity of the first body \[1.5\] times assuming a perfectly elastic impact. Then the ratio \[\frac{{{m}_{1}}}{{{m}_{2}}}\] is

    A)  \[\frac{1}{25}\]              

    B)         \[\frac{1}{5}\]

    C)  5                              

    D)         25

    Correct Answer: C

    Solution :

     As discussed in above problem\[=\frac{{{m}_{1}}-{{m}_{2}}}{{{m}_{1}}+{{m}_{2}}}=\frac{{{v}_{1}}}{{{v}_{2}}}\]                     \[=\frac{1}{1.5}=\frac{2}{3}\] or,          \[\frac{{{m}_{1}}-{{m}_{2}}}{{{m}_{1}}+{{m}_{2}}}=\frac{3}{2}\] Applying componendo and dividendo, we have          \[\frac{{{m}_{1}}}{{{m}_{2}}}=\frac{3+2}{3-2}=\frac{5}{1}\]


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