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JEE Main & Advanced JEE Main Solved Paper-2017

  • question_answer
    A body of mass \[m={{10}^{-2}}kg\]is moving in a medium and experiences a frictional force \[m={{10}^{-2}}kg\]Its intial speed is \[{{v}_{0}}=10m{{s}^{-1}}.\]If, after 10 s, its energy is\[\frac{1}{8}mv_{0}^{2},\]    JEE Main Solved Paper-2017

    A)  \[{{10}^{-4}}kg\,{{m}^{-1}}\]                     

    B) \[{{10}^{-1}}kg\,{{m}^{-1}}{{S}^{-1}}\]

    C)  \[{{10}^{-3}}kg\,{{m}^{-1}}\]                     

    D)  \[{{10}^{-3}}kg\,{{s}^{-1}}\]

    Correct Answer: A

    Solution :

     \[\frac{1}{2}mv_{f}^{2}=\frac{1}{8}mv_{0}^{2}\]                 \[{{v}_{f}}=\frac{{{v}_{0}}}{2}=5\,m/s\] \[({{10}^{-2}})\frac{dv}{dt}=-k{{v}^{2}}\] \[\int_{10}^{5}{\frac{dv}{{{v}^{2}}}}=-1000k\int_{0}^{10}{dt}\] \[\frac{1}{5}-\frac{1}{10}=100\,k(10)\] \[k={{10}^{-4}}\]


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