Water is lifted to a vertical height of 90 m using a 7.46 kW engine. If the efficiency of the engine is 80% , find the amount of water lifted in a minute.

Explanation

Let the mass fo water lifted per minute be m . Effective power of the engine `=7.46 xx10^3 xx0.8 W`
Now, work done per second = the effective power
`therefore (Fs)/t =(mgs)/t =7.46xx10^3 xx0.8`
or, `m=7.46 xx10^3xx0.8xxt/(gs)`
` =(7.46xx10^3xx0.8xx60)/(9.8xx90)`
`[because t=1` min =60 s , g=`9.8 m*s^(-2), s=90 m]`
`~~ 406 kg`