Example 15-1
Water is pumped through a 3 cm diameter pipe to an
elevated reservoir, as shown. The reservoir is very large;
therefore, the velocity of the top surface is approximately
zero. At a certain time, the height of water in the reservoir
is 290 cm above the level of the pump. Neglecting viscous
effects, calculate the power input to the pump.
Solution:
Begin by finding the pressure at point 2. From Bernoulli’s
equation
2
2
3
3
2
2
2
3
2
2
P
P
gz
gz
ρ
ρ
+
+
=
+
+
V
V
The velocity at point 2 can be determined using the
velocity at point 1 and conservation of mass.

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