Q. Ten litre of water per second is lifted from well through 20 m and delivered with a velocity of $10\ ms^{- 1}$, then the power of the motor is
A) 1.5 kW
B) 2.5 kW
C) 3.5 kW
D) 4.5 kW
Explanation
(b) $P = \frac{total\ energy}{t} = \frac{mgh + \frac{1}{2}mv^{2}}{t}$
$= \frac{10 \times 10 \times 20 + \frac{1}{2} \times 10 \times 10 \times 10}{1}$
$= 2000 + 500 = 2500\ W$
$= 2.5\ kW$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.