FIGURE 15-14
-Water flows out of a large reservoir through an open pipe, as shown in Figure 15-14. What is the speed of the water as it comes out of the pipe?
A) 8.86 m/s
B) 9.90 m/s
C) 12.5 m/s
D) 14.0 m/s
E) 15.6 m/s

Question

FIGURE 15-14 
-Water flows out of a large reservoir through an open pipe, as shown in Figure 15-14. What is the speed of the water as it comes out of the pipe?
A) 8.86 m/s 
B) 9.90 m/s 
C) 12.5 m/s 
D) 14.0 m/s 
E) 15.6 m/s

Quizplus · Accepted Answer

Using the Bernoulli equation:
P1 + 1/2 ρv1^2 + ρgh1 = P2 + 1/2 ρv2^2 + ρgh2
Since the water flows out of an open pipe, P1 = P2 = atmospheric pressure (101325 Pa)
Also, h1 = height of the water level in the reservoir = 120 m
h2 = height of the pipe above the ground = 0 m
ρ = density of water = 1000 kg/m^3
Solving for v2:
1/2 ρv1^2 + ρgh1 = 1/2 ρv2^2
v2 = √(2gh1)
v2 = √(2*9.81*120)
v2 = 15.6 m/s
Therefore, the answer is C.

FIGURE 15-14 -Water Flows Out of a Large Reservoir Through an Open