Q15  A pump on the ground floor of a building can pump up water to fill a tank of volume 30 min 15 min. If the tank is 40 m above the ground, and the efficiency of the pump is 30%, how much electric power is consumed by the pump ?

Answers (1)
D Devendra Khairwa

Mass of the water is :

                                           m\ =\ \rho v

or                                               =\ 30\times10^3 \ Kg

 Thus the output power is given by : 

                                           Power\ =\ \frac{Work\ done}{Time}

or                                                         =\ \frac{mgh}{t}

or                                                         =\ \frac{30\times 10^3\times 9.8\times 40}{900}

or                                                         =\ 13.067\times 10^3\ W

Also, we are given that efficiency is 30 per cent.

Thus the input power is :

                                                P_i\ =\ \frac{13.067}{\frac{30}{100}}\times 10^3

or                                                     =\ 43.6\ KW