An electric pump on the ground floor of a building takes 10 minute to fill a tank of 45 m
with water. The tank is 20 m above the water level. If electric power consumed by the pump is 30 kW then efficiency of the pump will be (density of water is 1000 kg/m
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Answer:
Here, Volume of water =30 m
3
t=15 min=15×60 s=900 s;Height,h=40 m
Efficiency, η=30%
Density of water =10
3
kg m
−3
∴ Mass of water pumped =Volume×Density
=(30 m
3
)(10
3
kg m
−3
)=3×10
4
kg
P
output
=
t
W
=
t
mgh
=
900 s
(3×10
4
kg)(10 ms
−2
)(40 m)
=
3
4
×10
4
W
Efficiency, η=
P
input
P
output
P
input
=
η
P
output
=
3×
100
30
4×10
4
=
9
4
×10
5
=44.4×10
3
W=44.4 kW.
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