Question

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

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

Answer 1

The correct option is A $800W$

We know,

$P=F.v$

And ,

$F=\frac{\Delta p}{\Delta t}=\frac{mv}{t}$

$P=\frac{m{v}^2}{t}=\frac{\rho V{v}^2}{t}=\frac{\rho Al{v}^2}{t}$

$\frac{l}{t}=v$

$P=\rho A{v}^3$

Also, $\rho A=\frac{m}{l}=100$

$P=\mu v^3$

$P=100\times 8=800W$

Option $\text{A}$ is the correct answer