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AFMC AFMC Solved Paper-2010

  • question_answer
    An open water tight railway wagon of mass \[5\times {{10}^{3}}kg\]coasts at an initial velocity of 1.2 ms-1 without friction on a railway track. Rain falls vertically downwards into the wagon. What change occurs in KE of the wagon, when it has collected 103 kg of water?

    A) 900 J                                     

    B) 300 J

    C) 600 J                                     

    D) 1200 J

    Correct Answer: C

    Solution :

    If v' is final velocity of wagon, then applying principle of conservation of linear momentum, we get, \[5\times {{10}^{3}}\times 1.2=(5\times {{10}^{3}}+{{10}^{3}})\times v'\] \[v'=1\,m{{s}^{-1}}\] Change in KE \[=\frac{1}{2}(6\times {{10}^{3}})\times {{1}^{2}}-\frac{1}{2}(5\times {{10}^{3}}){{(1.2)}^{2}}\] \[=600\,J\]


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