Fluid Flow Calculations: Understanding Flow Rate and Flow Speed

  • Thread starter edge
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In summary: Originally posted by edge Ahh silly me. This I see. But I still had points taken off (this is from a previous test), I guess for not having a flow speed. How exactly would I be able to find that with the given information? You are given the speed (275 cm/s) and cross-sectional area (10 cm^2). Go forth and multiply.You can use the continuity equation to find the flow speed.
  • #1
edge
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What's the difference between a fluid's flow rate and flow speed? I use the continuity equation to get the flow speed I thought but I couldn't think of how to get the rate. Here's the exact question if you want that for reference:

A liquid of density equal to 1.85 g/cm^3 flows through two horizontal sections of tubing joined end to end. In the first section (large section) the cross-sectional area is 10 cm^2, the flow speed is 275 cm/s, and the pressure is 1.2E5 Pa. In the second section (small section), the diameter of the tube is 2.5 cm.

-Find the flow speed, flow rate, and the pressure in the small tube section.

Thank you for your time and help!

-edge
 
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  • #2
Originally posted by edge
What's the difference between a fluid's flow rate and flow speed?
I believe flow speed is the speed of the fluid at some point, while flow rate is the quantity of fluid moving past a certain point. Flow rate depends on cross sectional area.
 
  • #3
Thanks.

Ahh, I can see the difference now...but no where in my physics book can I find an example of this. Is there an equation for finding it? Or does it involve some manipulation of the continuity or bernoulli's equation?
 
  • #4


Originally posted by edge
Ahh, I can see the difference now...but no where in my physics book can I find an example of this. Is there an equation for finding it? Or does it involve some manipulation of the continuity or bernoulli's equation?
The continuity equation is the flow rate equation! VA = the flow rate (volume per time). The continuity equation says that the flow rate is constant.
 
  • #5
Ahh silly me. This I see. But I still had points taken off (this is from a previous test), I guess for not having a flow speed. How exactly would I be able to find that with the given information? I'm at a loss :( just trying to figure it out before the final tomorrow. Fluids are the only thing that still gives me trouble =x Well, and some harmonic motion problems. So if you could point me in the right direction, I'd greatly appreciate it! Thanks again for your help.

-edge
 
  • #6
Originally posted by edge
Ahh silly me. This I see. But I still had points taken off (this is from a previous test), I guess for not having a flow speed. How exactly would I be able to find that with the given information?
You are given the speed (275 cm/s) and cross-sectional area (10 cm^2). Go forth and multiply.
 
  • #7
Yeah, I figured it out. Sorry for not responding soon enough. I was too used to using AV1 = AV2 to realize that AV is the flow rate. I just plugged in the numbers to get the flow speed in the smaller pipe and then multiplied my new speed with the crossectional area (found with the given diameter). Sorry for the trouble and my ignorance. Too much studying = sore brain. Thanks again.

-edge
 

1. What are fluids?

Fluids are substances that can flow and take on the shape of their container. They include liquids, gases, and plasmas.

2. What is the difference between a liquid and a gas?

Liquids have a definite volume and take the shape of their container, while gases have no definite volume or shape and will expand to fill their container.

3. How do fluids behave under different temperatures and pressures?

Temperature and pressure can affect the density, viscosity, and compressibility of fluids. For example, increasing temperature typically decreases the viscosity of a fluid, making it easier to flow.

4. What are some real-world applications of fluid mechanics?

Fluid mechanics is used in a variety of fields, including engineering, meteorology, and biology. Some common applications include designing pumps and turbines, predicting weather patterns, and understanding blood flow in the human body.

5. How do fluids play a role in our daily lives?

Fluids are essential for many everyday activities, such as drinking water, cooking, and transportation. They also play a role in natural processes, such as the water cycle and the movement of air in the atmosphere.

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