A pump on the ground floor of a building can pump of water to fill a tank of volume `30 ms^(3)` in `15 min`. If the tank is `40m` above the ground and the efficiency of the pump is `30 %` , how much electric power is consumed by the pump? `("Take" g = 10 ms^(2))`

Explanation

Volume of tank , `V = 30 m^(3) , g = 9.8 " m " s^(-2)`
Height , h = 40 m
Density of water ` = 1000 kg//m^(3)`
Mass = Volume `xx ` density
` = 30 xx1000 `
` m = 3 xx10^(4)` kg , Output Power ` = ("Work done ")/("time") = (mgh)/t`
`= (3 xx10^(4) xx 9.8 xx40)/(15 xx 60) `
` = (196000)/15 = 13066 W `
Percentage efficiency = `("Output power")/("Input power ") xx100`
Input power = `(13066 xx100)/30`
`= 43.6 kW ` .