Question

Water falls from a height of 50 m at the rate of 20 kg/s to operate a turbine. The
losses due to frictional forces are 20% of energy incident on the turbine. The
power generated by the turbine is (g = 10 ms-?)
mm
Select one:
O a. 8 kW
O b. 10 kW
O c. 12 kW
O d. 9 kW
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Answer 1

Answer:

Hope it will help you....

Answer 2

Answer:

The power generated by the turbine is 8kW.

Explanation:

Given the height of water fall, $h=50 m$

Rate of water fall to operate a turbine,  $\frac{m}{t}=20 kg/s$

The loss of energy due to frictional forces = 20%  

Acceleration due to gravity, $g = 10 m/s$

The efficiency of operating a turbine, $\eta=100-20=80\%$

The power generated by the turbine is input power times the efficiency of the turbine, i.e., $P=P_{in} \times \eta$                                                            ...(1)

Power is defined as work done per unit time. hence $P_{in} =\frac{W}{t}$        ...(2)

Work done is equal to energy stored, therefore, $W=mgh$             ...(3)

Combining the three equations,

$P=\frac{m}{t}gh \times \eta$

Substituting the respective values,

$P=20\times 10\times 50 \times\frac{80}{100}$

$=20\times 10\times 5 \times 8$

$= 8000W=8kW$

The power generated by the turbine is 8kW.

Hence, the correct answer is option a.