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I refer you all to the following web site to demonstrate the 
relationship between fluid (air) flow velocity and pressure.  It is 
quite nice for a "discrepant" event demo.
Francis Gardner

http://www.ceet.niu.edu/faculty/kostic/bernoulli.html

----- Original Message -----
From: Natasha Aristov <[log in to unmask]>
Date: Saturday, December 2, 2006 6:00 am
Subject: Flying and Bernouilli's principle

> ISEN-ASTC-L is a service of the Association of Science-Technology 
> CentersIncorporated, a worldwide network of science museums and 
> related institutions.
> 
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> 
> Uh-Oh.
> 
> Bernouilli's principle states, or rather observes, that the 
> pressure 
> in a moving fluid is lower than the pressure in a standing 
> fluid.  This is hard to believe at first glance, but I use the 
> analogy of cars on a freeway:  when they are moving fast, the 
> distance between them is larger (low pressure), when they are in a 
> traffic jam, the "car-fluid pressure" is high.
> 
> So much to Bernouilli.
> 
> The only ONLY way to get anything to fly is by making the air 
> pressure below the object higher than the air pressure above the 
> object.  It has nothing to do with wing SHAPE -- the wing shape 
> can 
> help make flying more efficient, but it is not decisive in whether 
> a 
> thing will fly.  Check out some pieces of trash one day on a windy 
> day.
> So:  you set up a pressure differential above and below a plane 
> wing.  You do this by moving the plane through the air at very 
> high 
> speeds so that the air gets shoved up under the forward part of 
> the 
> wing.  The wing blocks (part of) the air from flowing behind 
> it:  So  you have high pressure below and low pressure behind.
> 
> 
> SO.... it turns out (it is a CONSEQUENCE, not a cause!!!) that the 
> air particles below the wing are slower than the air particles 
> above the wing.
> 
> 
> Still don't believe this?:  a terrible, common "explanation" of 
> flight  is that because the wing is shaped the way it is, the air 
> above the wing has a longer distance to travel than the air below 
> the 
> wing.  So it moves faster to keep up.
> 
> WHAT????  How does air know how far it has to go?  And ... why 
> does 
> it need to keep up with the other air????
> 
> Bernouilli is OK, but it doesn't make planes fly.  Flying planes 
> make 
> Bernouilli.
> 
> 
> 
> But what do I know?  I'm just a chemist.
> 
> Natasha
> 
> 
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