Question

An engine pumps water through a hose pipe. Water passes through the pipe and leaves it with a velocity of $2 \,m/s$. The mass per unit length of water in the pipe is $100 \,kg/m$. What is the power of the engine?

• A. 400 W
• B. 200 W
• C. 100 W
• D. 800 W

Answer 1

Answer: (D)

800 W

Answer 2

Here,
Mass per unit length of water, $\mu = 100 \,kg/m$
Velocity of water, $v = 2 \,m/s$
Power of the engine, $P - \mu v^3$
$= (100 \,kg/m) (2 \,m/s)^3$
$= 800 \,W$