BCECE Engineering BCECE Engineering Solved Paper-2008

  • question_answer
    \[4{{m}^{3}}\]of water is to be pumped to a height of 20 m and forced into a reservoir at a pressure of \[2\times {{10}^{5}}N/{{m}^{2}}.\] The work done by the motor is (external pressure\[={{10}^{5}}\,N/{{m}^{2}}\])

    A) \[8\times {{10}^{5}}J\]  

    B)         \[16\times {{10}^{5}}\,J\]

    C)  \[12\times {{10}^{5}}\,J\]           

    D)         \[32\times {{10}^{5}}\,J\]

    Correct Answer: C

    Solution :

    Work done \[W=mgh+\Delta pV\] \[=V\rho gh+\Delta pV\]                 Here,\[V=4\,{{m}^{3}},\rho ={{10}^{3}}kg/{{m}^{3}},g=10\,m/{{s}^{2}},\] \[h=20\,m,\Delta p=(2\times {{10}^{5}}-1\,\times \,{{10}^{5}})N/{{m}^{2}}\] \[\therefore \]  \[W=4\times {{10}^{3}}\times 10\times 20\]                 \[+(2\,\times \,{{10}^{5}}-1\times {{10}^{5}})\times 4\]                 \[=8\times {{10}^{5}}+4\times {{10}^{5}}\] \[=12\times {{10}^{5}}\,J\]


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