Why does a hose have a wider flow at the end than at the beginning?

In summary: This is due to the conservation of mass.In summary, when water flows from a garden hose, the flow becomes wider at the beginning and then narrows as it descends. This is due to the increase in velocity and decrease in area, as a result of the conservation of mass. b) To calculate the time it takes for the diameter to halve and the distance the water has fallen, we can use the equation v^2=u^2+2as, where v is the final velocity, u is the initial velocity, a is the acceleration and s is the distance. In this case, the initial velocity is 0.1 m/s and the final velocity is unknown. The acceleration is due to gravity, which is
  • #1
bruceflea
11
0
Water flows from a garden hose. If the end of the garden hose is turned downward, a steady stream of water is seen to emerge from it. Upon closer observation, it can be seen that the flow of water is wide when it has just emerged from the hose pipe, and becomes more narrow as it descends (see Figure 5).

http://img4.imageshack.us/img4/9007/gardenhose8xh.th.png

Figure 5. Flow from a garden hose.


a) Explain why this happens.

b) If the water emerges from the tap with velocity u1 = 0.1 m/s, and the hosepipe diameter is 12 mm, calculate how many seconds it takes for the diameter of the water flow to halve, and calculate how far the water has fallen from the end of the hosepipe in that time.

c) If I open the tap further, put a nozzle on the end of the hosepipe with a diameter of 6 mm, and point it upwards, then the water reaches a maximum height of 2 metre above the end of the hosepipe. Calculate the water pressure in the hosepipe, assuming that the height difference between the hosepipe itself and the nozzle exit can be ignored.

I just need a little guidance with b and c.

For c, I think I'm supposed to take bernoullis between the exit of the nozzle and the height the water reaches to calculate the pressure at the nozzle exit. Then bernoullis between the exit and the hose pipe to calculate the hose pressure. But what I'm not too sure about is the column of water - is it reasonable to use bernoullis as I would if it was 2 metres of vertical pipe?

I've no idea where to start with b.
 
Last edited by a moderator:
Physics news on Phys.org
  • #2
b)Think of it this way...if you halved the area of the pipe, what velocity would the water have to be flowing? What was your answer to part A? Do you remember your basic mechanics equations with a constant acceleration?

c)You're on the right track. One hint you may want to look up...instead of the term "pressure" think of the term "head".
 
  • #3
For a,

Velocity of the water increases as there is no longer friction with the pipe. For a constant volumetric flow rate the area has to decrease as the velocity increases.
 

1. What is Bernoulli's principle?

Bernoulli's principle is a fundamental concept in fluid dynamics that states that as the speed of a fluid increases, the pressure within the fluid decreases. This principle is based on the law of conservation of energy.

2. How does Bernoulli's principle apply to hoses?

In the context of hoses, Bernoulli's principle explains why water sprays out of a hose with greater force when the nozzle is partially closed. As the cross-sectional area of the nozzle decreases, the water must speed up to maintain the same flow rate, resulting in a decrease in pressure and a more powerful spray.

3. What factors affect the application of Bernoulli's principle in a hose?

The key factors that affect Bernoulli's principle in a hose include the speed of the fluid, the density of the fluid, and the shape and size of the hose and nozzle.

4. Can Bernoulli's principle be used to explain the lift of an airplane wing?

Yes, Bernoulli's principle can be used to explain the lift of an airplane wing. As air flows over the curved shape of the wing, it must travel faster over the top of the wing in order to meet up with the slower moving air underneath. This creates an area of lower pressure on the top of the wing, resulting in lift.

5. Are there any limitations to Bernoulli's principle?

Bernoulli's principle is a simplified model that does not account for certain factors such as viscosity and turbulence. In addition, it only applies to incompressible fluids, so it may not accurately describe the behavior of gases. Therefore, while Bernoulli's principle is a useful concept, it has its limitations and should be applied with caution in real-world situations.

Similar threads

I Filling a pool with the hose end above or in the water
    • Classical Physics
Replies
10
Views
292
Engineering Water Flow from Pressurized Tank through Heat Exchanger
    • Engineering and Comp Sci Homework Help
2
Replies
56
Views
3K
Force of pressurized water exiting a hose or pipe?
    • Mechanical Engineering
Replies
20
Views
7K
I Find Best Water Nozzle Type & Pressure for Longest Distance
    • Mechanics
Replies
31
Views
3K
Bernoulli equation / fluid flow / finding height
    • Introductory Physics Homework Help
Replies
6
Views
1K
Fluid Mechanics- inviscid fluid pressure in a pipe
    • Engineering and Comp Sci Homework Help
Replies
11
Views
2K
Double experiment: "Falling ball viscometry" and viscous flow in an horizontal pipe
    • Engineering and Comp Sci Homework Help
Replies
31
Views
1K
Bernoulli’s Equation and External Forces
    • Introductory Physics Homework Help
Replies
4
Views
930
Maximum height for water from a fire hose
    • Introductory Physics Homework Help
Replies
4
Views
3K
Flow inside pipe, heat transfer
    • Engineering and Comp Sci Homework Help
Replies
15
Views
2K

Hot Threads

Recent Insights

Back
Top