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9th Class Science Work and energy Question Bank Work, Energy and Power

  • question_answer
    An engine of \[4.9\,\,kW\] power is used to pump water from a well which is \[20\,\,m\] deep. What quantity of water in kilolitres can it pump out in\[30\] minutes?

    A) \[45\,\,kl\]           

    B)        \[75\,\,kl\]

    C) \[25\,\,kl\]         

    D)        \[90\,\,kl\]

    Correct Answer: A

    Solution :

     Power \[=4.9\,\,kW=4900\] Watt Work done\[(30\,\,\min )=4900\times 30\times 60\,\,J\] If \[m\] is the mass of water in \[kg\] that is pumped out from a depth of \[20\,\,m\] in \[30\] minutes, then total work done for \[30\,\,\min =\]\[mgh=m\times 9.8\times 20\,\,J\] \[\therefore \]      \[4900\times 30\times 60=m\times 9.8\times 20\] \[\Rightarrow \]   \[m=\frac{4900\times 30\times 60}{9.8\times 20}=45k\,\,l\]


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