Question

Water falls from a height of $60m$ at the rate of $15kg/s$ to operate a turbine. The losses due to frictional force are $10$% of energy. How much power is generated by the turbine (in kW)?

• A. $8.1$
  
• B. $10.2$
  
• C. $12.3$
  
• D. $7.1$
  

Answer 1

The correct option is A $8.1$

Velocity just before hitting the turbine $=v=\sqrt{2gh}=\sqrt{1200}$

Energy transferred per unit time by the water to the turbine=Power delivered

$\Rightarrow 0.9\times (0.5\times m\times v^2)=0.9\times 0.5\times 15\times 1200=8100J/s=8.1kW$.

[0.9 is multiplied as there occur an energy loss of 10%]

Hence correct answer is option $A$