Question

Water falls from a height of `60 m` at the rate `15 kg//s` to operate a turbine. The losses due to frictional forces are `10%` of energy . How much power is generated to by the turbine? (g=10 m//s^(2))`.
A. 12.3 kW
B. 7.0 kW
C. 8.1 kW
D. 10.2 kW

Answer 1

Correct Answer - C
Energy used per `sec^(-1)` to operate turbine
`=mgh=15xx10xx"60 joule"`
= 9000 joule
Power supplied to turbine `=9000" joule sec"^(-1)`
Power loss due to friction = `"900 joule sec"^(-1)`
Power generated by turbine
`=(9000-900)"joule sec"^(-1)`
`"= 8100 joule sec"^(-1)=8.1 kW`
Second approach
`P_("generated")=P_("input")xx(90)/(100)=(mgh)/(t)xx(90)/(100)`
`=(15xx10xx60xx90)/(100)=8.1kW`