Q. A $10\ H.P.$ motor pumps out water from a well of depth $20m$ and fills a water tank of volume $22380\ litres$ at a height of $10\ m$ from the ground. The running time of the motor to fill the empty water tank is ($g = 10ms^{- 2}$)
A) $5\ minutes$
B) $10\ minutes$
C) $15\ minutes$
D) $20\ minutes$
Explanation
(a) Volume of water to raise $= 22380\ l = 22380 \times 10^{- 3}m^{3}$
$P = \frac{mgh}{t} = \frac{V\ \rho gh}{t} \Rightarrow t = \frac{V\ \rho gh}{P}$
$t = \frac{22380 \times 10^{- 3} \times 10^{3} \times 10 \times 10}{10 \times 746} = 5\ min$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.