Answer:
Mechanical power of pump is 74.07%.
Step-by-step explanation:
Power of motor = 15 KW
Efficiency of motor= 90%
So the actual power(P) supplied by motor = 0.9 x 15 KW
P=13.5 KW
Water flow rate = 50 L/s
Volume flow rate = 50 L/s
We know that

So

We know that pump is an open system and work input for open system can be calculated as
W=VΔP
ΔP is the pressure difference
V is the volume flow rate
So by putting the values
W=0.05 (300-100) (here ΔP=300 - 100=200 KPa)
W=10 KW
So mechanical power of pump
η =0.7407
Mechanical power of pump is 74.07%.