Question

A motor boat is having a steady speed of $20m{s}^{-1}$ If the water resistance to the motor boat is 600 N, then the power is:

• A. 12 kW
• B. 120 kW
• C. 9.8 kW
• D. 1200 kW

Answer 1

Answer: (A)

12 kW

Work done by the force $F$ through distance $dx$ is $dW=Fdx$

The power supplied in time $dt$ , $P=$ work done /time $=\frac{dW}{dt}=\frac{Fdx}{dt}=Fv=600\times 20=12000W=12kW$ (take as velocity $v=\frac{dx}{dt}$)