Question

a motor of 15 KW can lift 2 quintal of water from a height of 30 m in 1 minute .what will be the change in energy spent if efficiency is increased by 5%?​

Answer 1

Power=
time
energy
​

dP=
dt
dE
​

=
dt
dm
​
×g×h
As it will be useful power
Volume =30m
3

volume
mass
​
=density
mass=1000kg×30m
3

takes 10min to fill
∴
dt
dm
​
=
10×60
30000
​
kg/s
∴
dt
dm
​
=50kg/s
∴P=50×10×30
=15000W=15kw
totalP
15
​
×100=80 given by
total power =
8
150
​
kw (question efficiency)
=18.75kw