# What increases when water flows down in a pipe: pressure, speed or both?

• cristipiticul
In summary, the student is trying to figure out how the different factors affect the velocity of water. He finds references to friction and pressure in liquids, discusses how those effects might be seen in a real world situation, and provides some links for further research.
cristipiticul
Hello!

I am working on a project with a classmate. We have a bucket which represents the water supply and an extensible hose. The bucket is hanged with a rope somewhere high. Here's how it works: the water from the bucket goes down the hose, spins a fan and then gets out of this system.

We are asked to provide documentation and research, but I don't know where to search for such things.

Firstly, I don't know what increases, the velocity, the pressure or both? I guess it's the velocity because if we think of two solids dropped from the same height, the second one dropped a short time later than the first one, they would never touch each other, so there's no pressure. But if we consider the friction between the water and hose, then the pressure will increase too. Furthermore, in my case the water flows at an angle, not freely like up-down.

Can the friction and the force of the water (which hits the fan) be calculated somehow?

Thanks for reading this!
cristipiticul

Last edited:
Here are some questions that might help you get started:

If you drain the entire bucket, using a stopwatch to measure how long it takes drain, and then clock how long it takes for all of that water to arrive at the bottom of the hose, do the times come out different, or the same? Also, if you attach your fan at the top of the hose, rather than the bottom, will it spin at a different speed?

Hope this helps.

The friction in a liquid is parameterized in terms of viscosity.
http://en.wikipedia.org/wiki/Viscosity
For a real world hose, the viscosity is not a negligible effect and should be included. You need to make some assumptions on the boundary between the water and the hose. Perhaps, you can assume that the water next to the hose is stationary (stuck to the hose) and there is a flow gradient as you move toward the center of the hose. You can solve for the flow velocity as a function of pressure using a differential equation based on the viscosity of water. Probably, this has already been done somewhere, so you just need to find a source to cite.

What level of school are you at? If fluid equations are over your head, then you might be able to treat the hose as a resistor, if the hose is small enough or long enough.

We are asked to provide documentation and research, but I don't know where to search for such things.

You might start here.

http://hyperphysics.phy-astr.gsu.edu/hbase/pman.html

The second photo shows nicely how pressure and velocity are related.

Click on the blue "Bernoulli effect" near that picture and it takes you here :
http://hyperphysics.phy-astr.gsu.edu/hbase/pber2.html#pl
another graphic showing effect of pressure drop due to friction along your pipe.

You'll need to transpose your thinking to vertical pipes of course but you'll have no troubles.As an experiment, get one of those streamlined garden hose nozzles for the end of your hose, the simple one with non-adjustable tapered snout. They look like a miniature fire hose nozzle and the smaller the better.
Point it straight up and see how nearly the stream approaches the water level in your bucket. Photograph it with your cellphone for various bucket heights.

The terms in those links shold enable youto reap rich information via google searches.

What a great excuse to play in the yard - "It's my physics homework, honest ! ".

The weather is warming so get wet and have some fun !

,

Thank you for reaching out and sharing your project with me! I can help provide some information and research on what increases when water flows down in a pipe.

The answer to your question is that both pressure and speed increase when water flows down in a pipe. This is due to the principles of fluid dynamics, which explain how liquids like water behave when they are in motion.

As water flows down a pipe, it is subjected to two main forces: gravity and friction. Gravity pulls the water down, while friction between the water and the walls of the pipe slows it down. However, as the water moves through the pipe, it also experiences changes in pressure.

When water flows through a narrower section of the pipe, the space for the water to move through is reduced, causing an increase in pressure. This is known as Bernoulli's principle, which states that as the velocity of a fluid increases, its pressure decreases. So, as the water moves through the pipe and its velocity increases, the pressure decreases. However, when the water reaches a wider section of the pipe, the pressure increases again as the velocity decreases.

In your project, the water is also flowing at an angle, which can affect the pressure and velocity of the water. The angle of the water flow can create changes in pressure and velocity, as the water is forced to change direction. This can also cause turbulence in the water, which can increase both the pressure and velocity.

As for calculating the friction and force of the water hitting the fan, this can be done using mathematical equations and formulas that take into account factors such as the size and shape of the pipe, the velocity of the water, and the properties of the fan. However, this may require some advanced knowledge of fluid dynamics and physics.

In terms of finding more information and research on this topic, I would recommend starting with reputable scientific sources such as textbooks, journals, and online databases. You can also consult with a physics or engineering professor or visit your local library for more resources.

I hope this helps and good luck with your project! Keep exploring and asking questions, as that is the heart of scientific inquiry.

## 1. Does pressure increase when water flows down in a pipe?

Yes, pressure increases when water flows down in a pipe. This is because as the water flows, it exerts a force on the walls of the pipe, which in turn increases the pressure inside the pipe.

## 2. Does speed increase when water flows down in a pipe?

Yes, speed increases when water flows down in a pipe. This is because as the water moves down the pipe, it gains kinetic energy, which results in an increase in speed.

## 3. Can both pressure and speed increase when water flows down in a pipe?

Yes, both pressure and speed can increase when water flows down in a pipe. As mentioned before, the pressure increases due to the force exerted by the water on the walls of the pipe. At the same time, the speed also increases due to the gain in kinetic energy.

## 4. Does the increase in pressure and speed occur at the same rate?

No, the increase in pressure and speed do not occur at the same rate. While the pressure increases due to the force exerted by the water, the speed increases due to the gain in kinetic energy. The rate at which these two factors increase can vary depending on the size and length of the pipe, as well as the flow rate of the water.

## 5. Is there a maximum limit to the increase in pressure and speed when water flows down in a pipe?

Yes, there is a maximum limit to the increase in pressure and speed when water flows down in a pipe. This limit is determined by the size and length of the pipe, as well as the flow rate of the water. It is important to ensure that the pressure and speed do not exceed this limit to prevent any potential damage to the pipe or its surroundings.

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