An electric pump is used to fill an overhead tank of capacity `9m^(3)` kept at a height of 10 m above the ground. If the pump takes 5 min to fill the tank by consuming 10 kW power, the efficiency of the pump should be (Take `g=10ms^(-2)`)

Options

A. A)`60%`
B. B)`40%`
C. C)`20%`
D. D)`30%`

Answer

D

Explanation

Work done in raising water = mgh
or W = `("volume "xx" density")gh`
`=(9xx1000)xx10xx10`
or `W=9xx10^(5)J`
`therefore` Useful power `=("work")/(t)`
`=(9xx10^(5))/(5xx60)=3kW`
Hence, efficiency = `("useful power")/("consuming power")`
`=(3)/(10)=30%`