Bernoulli's Principle Demo: Levitated Balls

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This is a demonstration of the role of Bernoulli's principle in stabilizing a ball held up by a vertical stream of air.

This demonstration was created at Utah State University by Professor Boyd F. Edwards, assisted by James Coburn (demonstration specialist), David Evans (videography), and Rebecca Whitney (closed captions), with support from Jan Sojka, Physics Department Head, and Robert Wagner, Executive Vice Provost and Dean of Academic and Instructional Services.

Physics Demos

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At 1:55; Another video with *the most common misconception in fluids.*
..
The centering is caused by the *acceleration* of the curved flow and is called the Coanda Effect, NOT Bernoulli's Principle.
..
The statement at time 1:55 is *Incorrect* --> : "If you have a high velocity, a high airspeed, then you nave a low pressure." <-- That is false.
..
Bernoulli's Principle correctly stated is: "An increase in speed is accompanied by a decreasing pressure.":
An increase in speed is an acceleration!
*An increase in speed is acceleration, not simply fast.*
.
Bernoulli's Principle becomes relevant at the place where the air is accelerated to teh higher speed.
..
You cannot compare some "fast" air with any random near-by 'slower' air for the pressure difference. The air must be accelerated.
.
Then, it is the pressure difference for the flow that *causes* the acceleration.
..
Other common demos are also misunderstood and misinterpreted are blowing over a curved paper, between two balloons or two cans. Those are all curved flow: Coanda Effect.
.
This simply parrots incorrect science.
..
For better information and demos anyone can easily duplicate see Weltner:
Weltner in PDF - "Misinterpretations of Bernoulli's Law".
Read the text and focus on these figures. :

Fig 3 "Fast" air, *NO PRESSURE REDUCTION.*
Figs 8 & 9 Curved (accelerated flow) Pressure change.

Please stop teaching bad science.
.

Here's videos that got it right:

Observer

The entire Utah State University team that put this on gets an A+ 👏

michaelornelas

If i had a teacher like you in my school days, I would have worked in nasa🤩

alphaace-pubgmobile

Thanx A lot sir!

Your demonstrations literally helping me in understanding concepts. 🔥🙏

helixjee

At 1:55; Another video with *the most common misconception in fluids.*
..
The centering is caused by the *acceleration* of the curved flow and is called the Coanda Effect, NOT Bernoulli's Principle.
..
The statement at time 1:55 is *Incorrect* : "If you have a high velocity, a high airspeed, then you nave a low pressure." *<-- That is false.*
..
Bernoulli's Principle correctly stated is: "An increase in speed is accompanied by a decreasing pressure.":
An increase in speed is an acceleration!
*An increase in speed is acceleration, not simply fast.*
.
Bernoulli's Principle becomes relevant at the place where the air is accelerated to the higher speed.
..
You cannot compare some "fast" air with any random near-by 'slower' air for the pressure difference. The air must be accelerated.
.
Then, it is the pressure difference for the flow that *causes* the acceleration.
..
Other common demos are also misunderstood and misinterpreted are blowing over a curved paper, between two balloons or two cans. Those are all curved flow: Coanda Effect.
.
This simply parrots incorrect science.
..
For better information and demos anyone can easily duplicate see Weltner:
Weltner in PDF - "Misinterpretations of Bernoulli's Law".
Read the text and focus on these figures. :

Fig 3 "Fast" air, *NO PRESSURE REDUCTION.*
Figs 8 & 9 Curved (accelerated flow) Pressure change.

Please stop teaching bad science.
.

Here's videos that got it right:

This one has it 100% correct!

The water curving around to the top wants to go straight. It's inertia lowers the pressure on the inside of the curve keeping it in the stream. It is explained better here when a fluid follows a convex curved surface:
..
This one s also correct.

Veritasium. He doesn't explain it completely well.

Observer

After watching tons of lectures I finally understand

wypy

At 1:55; Another video with *the most common misconception in fluids.*
..
The centering is caused by the *acceleration* of the curved flow and is called the Coanda Effect, NOT Bernoulli's Principle.
..
The statement at time 1:55 is *Incorrect* : "If you have a high velocity, a high airspeed, then you nave a low pressure." *<-- That is false.*
..
Bernoulli's Principle correctly stated is: "An increase in speed is accompanied by a decreasing pressure.":
An increase in speed is an acceleration!
*An increase in speed is acceleration, not simply fast.*
.
Bernoulli's Principle becomes relevant at the place where the air is accelerated to the higher speed.
..
You cannot compare some "fast" air with any random near-by 'slower' air for the pressure difference. The air must be accelerated.
.
Then, it is the pressure difference for the flow that *causes* the acceleration.
..
Other common demos are also misunderstood and misinterpreted are blowing over a curved paper, between two balloons or two cans. Those are all curved flow: Coanda Effect.
.
This simply parrots incorrect science.
..
For better information and demos anyone can easily duplicate see Weltner:
Weltner in PDF - "Misinterpretations of Bernoulli's Law".
Read the text and focus on these figures. :

Fig 3 "Fast" air, *NO PRESSURE REDUCTION.*
Figs 8 & 9 Curved (accelerated flow) Pressure change.

Please stop teaching bad science.
.

Here's videos that got it right:

This one has it 100% correct!

The water curving around to the top wants to go straight. It's inertia lowers the pressure on the inside of the curve keeping it in the stream. It is explained better here when a fluid follows a convex curved surface:
..
This one s also correct.

Veritasium. He doesn't explain it completely well.

Observer

The common misconception is that any moving air, such as from a hair dryer, leaf blower or your mouth, has a lower static pressure than the stationary air around it. This is not true and comes from a misreading of Bernoulli’s Principle and misunderstanding of how to apply it. There are several demonstrations that are misinterpreted to show the static pressure is lower.

The moving stream of air from one of these is at the very same static, atmospheric pressure as the still air around it. It is NOT lower.

Here is the correct explanation.

This moving air has MORE total energy than the still air around it, not the same amount. This additional energy was added by the blower. The Total energy is the potential energy of the atmospheric pressure plus the kinetic energy of its motion or momentum.

Each of these ‘blowers’ adds energy to the air in the form of static pressure. This internal pressure is higher than the atmospheric pressure outside it.

For example, muscles move the diaphragm to squeeze the lungs. This increases pressure in the lungs.

This internal pressure pushes more on the air than the pressure outside
A pressure difference between two locations is called a Pressure Gradient. This reflects the idea that the pressure changes gradually between the two locations.

Because the internal pressure pushes more on the air, there is a net force toward the lower pressure outside the blower. The air is free to move and is accelerated toward the lower pressure. This is Newton’s Laws in fluids.

Air has mass. A Pressure Gradient provides a net force. Mass is accelerated away from the higher force, toward the lower force and gains speed in this case. This happens at the outlet of the blower and we have the stream of air starting internally at the higher pressure and accelerating to atmospheric pressure.

That’s it.

For those watching the conservation of energy rules, the TOTAL energy of air INSIDE the blower is the same as the TOTAL energy of the stream OUTSIDE the blower. The trip from inside to outside has no energy changes in that air.

We see that inside the lungs, all the air has nothing but potential energy in the form of static pressure and no motion with kinetic energy – no dynamic pressure. All the energy in the lungs is in the potential energy of static pressure.

The air gains speed (acceleration) as it exits, thus changing the extra potential energy of pressure into kinetic energy of the moving momentum of the air’s mass.

Observer

Does anyone know where I can obtain one of the demonstration devices that he uses at the beginning of the video. It looks like a children's toy.

hopehenderson