Question

A pump draws water from a tank which is at $2.5m$ down from outlet and issues it from the end of a hose which the water is drawn. The cross sectional area is $10c{m}^2$, and the water leaves the end of the hose at a speed of $5m/s$. What is the rate at which the pump is working ?

• A. 100 W
• B. 185 W
• C. 96 W
• D. 200 W

Answer 1

Answer: (B)

185 W

$P=(gh+\frac{v^2}{2})\frac{dm}{dt}$

where $\frac{dm}{dt}=A\times V=10\times {10}^{-4}\times {10}^{-3}\times 5=5kg/s$

$=(9.8\times 2.5+\frac{25}{2})\left(5\right)$

$=185W$