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BHU PMT BHU PMT (Mains) Solved Paper-2006

  • question_answer
    The energy supplied to Kolkata by the state electricity board during an average November week day was 40 GWh. If this energy could be obtained by the conservation of matter, how much mass would have to be annihilated?

    A)  1.6 g                                     

    B)  2.2 g

    C)  4.0 g                                     

    D)  1.6kg

    Correct Answer: A

    Solution :

                     \[E=40GWh=(40\times {{10}^{9}}J/s)\] \[(60\times 60s)=1.44\times {{10}^{14}}J\] But         \[E=m{{c}^{2}}\] so,          \[m=\frac{E}{{{c}^{2}}}=\frac{1.44\times {{10}^{14}}}{{{(3\times {{10}^{8}})}^{2}}}=1.6\times {{10}^{3}}kg\] i.e.,        \[m=1.6g\]


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