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NEET NEET SOLVED PAPER 2019

  • question_answer
    Body A of mass 4m moving with speed u collides with another body B of mass 2m, at rest. The collision is head on and elastic in nature. After the collision the fraction of energy lost by the colliding body A is:                    [NEET 5-5-2019]

    A) \[\frac{4}{9}\]              

    B)   \[\frac{5}{9}\]

    C) \[\frac{1}{9}\]                          

    D) \[\frac{8}{9}\]

    Correct Answer: D

    Solution :

    \[{{v}_{2}}=\frac{{{m}_{1}}+{{u}_{1}}+{{u}_{2}}({{m}_{2}}-{{m}_{1}})}{{{m}_{1}}+{{m}_{2}}}\] \[{{v}_{2}}=\frac{2(4m)u+0}{6m}\] \[{{v}_{2}}=\frac{4}{3}u\] \[\frac{\Delta E}{E}=\frac{\frac{1}{2}2mv_{2}^{2}}{\frac{1}{2}4m{{u}^{2}}}=\frac{{{\left( \frac{4}{3}u \right)}^{2}}}{2{{u}^{2}}}=\frac{8}{9}\]


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