Bernoulli's Principle: Air Foil and Pieces of Paper
Вставка
- Опубліковано 11 вер 2024
- Bernoulli's priciple is demonstrated by holding a piece of paper and blowing air over the top surface. The piece of paper is observed to rise. Also, air is blown between two pieces of paper which are observed to move toward one another. The application of Bernoulli's principle to an air foil is described with the aid of a model airplane.
Equipment
- Pieces of paper
- Airplane model
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This video is part of the project "Videos of Physics Demonstrations", which is created by Dr. Galli and Dr. Amiri of Physics Department, Weber State University. To access the full library of the videos, please visit this link: www.weber.edu/...
Links to University and Department:
Weber State University Homepage: www.weber.edu/
WSU Physics Department: www.weber.edu/...
Believe it or not, most of this explanation is incorrect. @Observ45er is correct. I'm amazed at how often it is taught, even on a college level, that higher velocity "creates" lower pressures. It wasn't until recently that I discovered this is not exactly true. If something doesn't make sense in your mind, question it. That's what I finally did because it never made sense to me that more velocity causes less pressure; yet, this is how we were always taught that planes were able to fly. There are actually a couple different principles that create lift on plane wings. Lower pressure zones above wings do have something to do with it, but it's not created by higher velocity.
you are right, that's exactly what was running through my mind.
This Bad Bernoulli nonsense is SO frustrating. And here is a University "Professor" teaching it.
He has another one here where he accidentally "discovered another Bernoulli effect. . . . :
ua-cam.com/video/AnDvjjPQCuE/v-deo.html
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That one is is due to entrainment of the ring of water around the blunt rim of the nozzle exit.
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I'll try to contact him or the ASU physics department. . .
NO! The Coanda Effect is demonstrated by blowing above the paper.
Bernoulli is demonstrated by the *higher pressure* in his lungs accelerating the air out into the lower and normal atmospheric pressure in the room. The air out of his lips is AT ATMOSPHERIC pressure.
Thank you! You have really helped me
It is incorrect.
The speed of the flow is not *increasing* as it flows above the paper., therefore, the pressure is not dropping.
thank you sir. very well explain
Unfortunately wrong.
E
I can't believe they still teach this BAD SCIENCE at this level.!.!
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Bernoulli's Principle is *not* about "fast" air, it is about *increasing speed* which is *acceleration* that is *accompanied by* a pressure decrease along the path.
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WHY? What is the science behind this?
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Because:
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The higher pressure behind the flow pushes (accelerates) the air to a higher speed into the lower pressure region. Pressure gradients (differences across space) are the force that accelerates the mass of fluid.
A higher pressure region pushes (a force) the fluid (a mass) toward any and all nearby lower pressure regions. F=MA
This is simply Newton in fluids.
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PLEASE note that he starts quoting it correctly when he says: "As the speed increases". AS IT INCREASES!! Not after it increases! [and is already slowing down as it mixes with the still air]
*WHERE* is the speed actually "increasing" ?? Why, it is Inside his mouth, right at his lips!! This is where the Pressure Gradient exists and this is where the acceleration occurs.
The "high" pressure is inside and the "low" pressure is the outside normal atmospheric pressure.
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This is so flippin' obvious, I can't for the life of me, figure out why so many supposedly intelligent "science" people can't figure this out !!
Sooooo many people simply repeat this nonsense with absolutely no understanding at all...
That is not what is happening above the curved paper.
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The paper rises because:
Viscosity causes it to follow the curved path.
A curved path is an acceleration, right?
A low pressure is created by the *curved flow* because it wants to go straight (Newton's First) and this is called the Coanda Effect.
It will subsequently 'stay' out horizontally due to the viscosity caused entrainment.
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Bernoulli comes into play inside your mouth. The higher pressure there accelerates the air to a higher speed into the lower atmospheric pressure outside.
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The static pressure of that moving (but not speeding up) air OUTSIDE your mouth is at the SAME pressure as the still air all around it.
This can easily be measured. Weltner shows how:
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Weltner in PDF - "Misinterpretations of Bernoulli's Law".
Fig 3 is the fast air only.
Fig 7 is the viscosity requirement above a wing (NOT Coanda even though it looks like it).
SEE Figures 6 & 7 are upper surface. Figures 3 & 8 Lower pressure:
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user.uni-frankfurt.de/~weltner/Misinterpretations%20of%20Bernoullis%20Law%202011%20internet.pdf
you don't need to be selfish
@@mrkitteh7611 Comments like that add nothing and quite frankly, that one doesn't make sense. I' didn't take anything. much less, too much of anything.
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I provide science well known by professionals in the field of fluid dynamics. This video shows incorrect information as I explained. If there something that you don't understand, ask questions.
I am willing to help understand the correct science
if the informatino and reference I provided seem unclear.
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I don't know what to put in my assignment now-
@@fern.quitx_x8645 Welcome to real life.
You put down what your teacher _wants_ you to put down, for the grade.
Whether you like it or not, many teachers are wrong about this, but they give the grade.
What does you teacher say? Use that!
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However...
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Real science follows...
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PLEASE note that he starts quoting it correctly when he says: "As the speed increases". *AS* IT INCREASES!! Not after it increases! [and is already slowing down as it mixes with the still air]
*WHERE* is the speed actually "increasing" ?? Why, it is Inside his mouth, right at his lips!! This is where the Pressure Gradient exists and this is where the acceleration occurs.
The "high" pressure is inside and the "low" pressure is the outside normal atmospheric pressure.
..
This is so flippin' obvious, I can't for the life of me, figure out why so many supposedly intelligent people can't figure this out !!
Sooooo many people simply repeat this nonsense with absolutely no understanding at all.
@@Observ45er
ok-