# How am i supposed to determine the speed of air?

• MolotovMonarch
In summary, determining the speed of air can be done through a few different methods. One way is by using an anemometer, which measures the wind speed by rotating in the wind. Another method is by using a hot wire anemometer, which measures the speed of air by detecting changes in temperature caused by the air flow. Additionally, the speed of air can also be calculated using the Bernoulli's equation, which takes into account the density and pressure of the air. Ultimately, the most accurate way to determine the speed of air may depend on the specific situation and the level of precision needed.
MolotovMonarch

How am i supposed to determine the speed of air??
I need it for Bernoulli's Equation, see i built a glider and i have to present on Wednesday, and i want to show that i did at least one calculation.
As if things weren't bad enough already i have to figure out two velocities, one of the speed underneath the wing and the other of the velocity on top of the wing.
how do i do it?? I was thinking that maybe the velocity of the air over the wing is the whole glider's velocity which would be really easy to calculate. and perhaps the velocity of the air underneath the wing would be the air's velocity at that time. (i can probably get it online at a weather website)
Anyone have any suggestions?? R.S.V.P.!
This is driving me nuts!

MolotovMonarch said:
How am i supposed to determine the speed of air??
I need it for Bernoulli's Equation, see i built a glider and i have to present on Wednesday, and i want to show that i did at least one calculation.
As if things weren't bad enough already i have to figure out two velocities, one of the speed underneath the wing and the other of the velocity on top of the wing.
how do i do it?? I was thinking that maybe the velocity of the air over the wing is the whole glider's velocity which would be really easy to calculate. and perhaps the velocity of the air underneath the wing would be the air's velocity at that time. (i can probably get it online at a weather website)
Anyone have any suggestions?? R.S.V.P.!
This is driving me nuts!
Tell your teacher that Bernoulli's principle does not explain lift. Have a look at:
http://www.grc.nasa.gov/WWW/K-12/airplane/wrong1.html

You might try calculating the lift that your glider creates. Have a look at the NASA site on glider flight:

http://www.grc.nasa.gov/WWW/K-12/airplane/glider.html

AM

hmm.. the bernoulli principle doesn't explain lift... so what does?

newbie101 said:
hmm.. the bernoulli principle doesn't explain lift... so what does?

What does what?

What does explain lift?----> Fluid Mechanics Theory.

What does Bernoulli Equation say?----> Several things, but not everything.

Bernoulli principle does explain the lift, the problem is that you cannot use Bernoulli equation to calculate the lift.
Bernoulli equation deals with ideal nonviscous liquid. For that liquid no lift can be generated, neither air can provide a retarding force. However, if the viscousity is taken into account, the flow became complex.
The rough explanation is that at relativelly low speeds vortecies are forming on the rear edge of a wing. Then, because the momentum should be conserved, an opposite vortex is formed along the wing. That attached vortex provide the necessary difference of the air speeds above and below the wing. After that we can use the Bernoulli principle to calculate the lift.
That theory was developed by Zhukovsky and Chaplygin in Russia before WWI.

shyboy said:
Bernoulli principle does explain the lift, the problem is that you cannot use Bernoulli equation to calculate the lift.
Bernoulli equation deals with ideal nonviscous liquid. For that liquid no lift can be generated, neither air can provide a retarding force. However, if the viscousity is taken into account, the flow became complex.
The rough explanation is that at relativelly low speeds vortecies are forming on the rear edge of a wing. Then, because the momentum should be conserved, an opposite vortex is formed along the wing. That attached vortex provide the necessary difference of the air speeds above and below the wing. After that we can use the Bernoulli principle to calculate the lift.
That theory was developed by Zhukovsky and Chaplygin in Russia before WWI.

You're exposing yourself to replies of Arildno & Co. who has been discussing this topic very long long before. I am not going to reply to you in order to don't start it again.

Clausius2 said:
You're exposing yourself to replies of Arildno & Co. who has been discussing this topic very long long before. I am not going to reply to you in order to don't start it again.
Am I a dangerous man? :uhh:
Can't say I disagree terribly much with shyboy, since he notes the crucial importance of viscosity.

Last edited:
I believe it is better to be exposed to critics than to be safe like this:
What does explain lift?----> Fluid Mechanics Theory.

why not Newton's laws ;)

Easy guys - this looks like a question that needs a simple answer. MM - how about just using Bernoulli's equation to calculate the freestream velocity of the air(essentially, the airspeed of the glider) at the front of the glider by measuring the pressure with a pitot tube: http://www.du.edu/~jcalvert/tech/fluids/bernoul.htm

well thanks guy for trying to help, but i don't really need it anymore. I have to present on Wednesday and I'm not really worried about it cus I'm pretty much done...i just got to do the PowerPoint presentation.

and by the way, you can find the NetForce using Bernoulli's Equation.
First you take the change in pressure using Bernoulli's equation.
Then, since Pressure is equal to Force over Area, you solve for force and get
F=(pressure)(A) the area used is the wing's total area. you calculate Fnet and Voila, you're done!
we did an example problem like this, and if the teacher was wrong you better not ride in another Boeing cus that's where he worked. hahaha

arildno said:
Am I a dangerous man?

You know, Arildno, you have a Toledan Knife just below your PC table. I saw it when you invited me to take dinner that day...

Toledan knife?
Are you sure you don't mean the saracen sword my Viking ancestor got from Al-Mansur for helping to subjugate soft Spaniards of his time?

arildno said:
Toledan knife?
Are you sure you don't mean the saracen sword my Viking ancestor got from Al-Mansur for helping to subjugate soft Spaniards of his time?

:rofl: :rofl: Not really.

Toledo is a medieval city of Spain. It is famous for its steel and swords:

"All European armies knew the superior quality of Toledo's steel and many great warriors relied only on sabers of Toledan provenance."
go here:
http://www.tf.uni-kiel.de/matwis/amat/def_en/articles/steel_collector/swords_from_toledo.html

The best steel? In Toledo. The best swords? In Toledo.

Some time you come here I will show Toledo to you, if you want.

## 1. What tools do I need to determine the speed of air?

To determine the speed of air, you will need an anemometer. An anemometer is a scientific instrument that measures wind speed and direction. It consists of a small propeller that rotates in the wind, and the rotation speed is then converted into a measurement of wind speed.

## 2. How do I use an anemometer to measure air speed?

To use an anemometer, you should hold it in an open area with no obstructions and allow the propeller to rotate freely. Depending on the type of anemometer, you may need to hold it in a specific direction to get an accurate reading. Once the propeller has stopped moving, you can record the wind speed measurement.

## 3. Can I determine the speed of air without using an anemometer?

There are other methods to estimate the speed of air, such as using a windsock or observing the movement of objects in the wind. However, an anemometer is the most accurate and reliable tool for measuring air speed.

## 4. How does air speed affect weather conditions?

Air speed is a crucial factor in determining weather conditions. Higher wind speeds can result in more severe weather, such as storms and hurricanes. Wind speed also plays a role in temperature and humidity levels, as it can affect how quickly air moves and circulates in the atmosphere.

## 5. What units are used to measure air speed?

The most common unit of measurement for air speed is meters per second (m/s). However, other units such as miles per hour (mph) and kilometers per hour (km/h) are also used. In some cases, knots (nautical miles per hour) may be used, especially in marine and aviation industries.

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