Re: [Phys-l] Bernoulli Effect

[Peter Schoch <pschoch@nac.net>]

OK, even Algebra-based college physics students ask this kind of  
thing; so, let me give this a try...

Let's look at 2 particles, one goes over the wing, and one goes  
under.  If the one going under the wing goes faster (shorter distance  
and shorter time) it gets to the end of the wing first, while the  
other particle is still over the top of the wing.

This makes the next 2 particles do the same.  After a while the  
particles will 'back up' on top of the wing.  If that were the case,  
the density would have to become greater over the wing, pushing down  
more on the wing, and it would not fly!

Since this clearly doesn't happen, we can appeal to the equation of  
continuity and Bernoulli's equation to 'rectify' this problem by  
showing that the particles over the top must go faster, which means  
the top pressure is lower.

Does that help/work?

Peter Schoch
SCCC

On Dec 15, 2007, at 1:59 PM, David Abineri wrote:

> In describing the Bernoulli effect to high school students I  
> invariably
> get stuck on one particular question and I wonder if someone can help
> give me the "high school" words necessary to answer this question.
>
> When looking at the cross section of a wing, I have always said that  
> the
> air flow under the wing (which is a relatively flat surface) is slower
> than the air flow over the top of the wing which is curved.  The
> question from them is "why isn't it just as likely that he air over  
> the
> top of the wing does not speed up and simply takes a longer time to
> travel the longer distance over the curved section of the wing?".
>
> Any assistance would be welcome.  Thanks,    David Abineri
>
>
>
> --
> D. Abineri     dabineri@fuse.net
>
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