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Date: | Sat, 2 Dec 2006 10:22:41 -0500 |
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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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