COMEDK Exam 2014 Solved Paper

Volume of water in tank, V=30m3
Time taken to fill the tank,
t=15min=15×60=900s
Height of the tank, h=40m
∴ Mass of pumped water, m= Vohme × Density of water
=30×103=3×104kg
Work done by the pump to fill the tank,
W=mgh
=3×104×10×40
=1.2×107J
∴ Output power of the pump,
Po=

W

t

=

1.2×107

900

=

4

3

×104W
As we know, effeciency =

Output‌power(Po)

Input‌Power(Pi)

⇒ 0.3=

4 3 ×104

Pi

⇒ Pi=

4×104

3×0.3

=4.4×104W=44kW