Re: [Phys-l] Bad physics in National park

["Richard Tarara" <rbtarara@sprynet.com>]

I don't want to get into the wing thing for the umpteenth time, but flying 
upside down involves different physics than Bernoulli lift.  However it 
works, a wing (such as the Wright Brothers or various recent human-powered 
craft) can _probably_  be modeled using Bernoulli at least in part, but 
upside down flight pretty much requires a conservation of momentum 
argument--like sticking your hand out the window of a moving car and placing 
the fingers slightly upwards so that the the palm hits the air--forcing it 
down and the hand up.  The only point here is that upside-down flight 
doesn't, in itself, disprove any Bernoulli explanation.  ;-)

Rick (who would guess that the Wright flyer can't fly upside down, but also 
recalls a Bernoulli like explanation for wings presented at the Air Force 
museum in Dayton!)




----- Original Message ----- 
From: "Donald Smith" <dsmith4@guilford.edu>


> Hi,
>
> No, that explanation makes more sense than what they said at the national
> park.
> What they said at the park was more like "the air that goes over the top 
> of
> the
> wing has to travel further than the air going under the bottom of the 
> wing.
> The
> two flows must travel across the wing in the same amount of time.
> Therefore,
> the top one must travel faster, and since it is travelling faster, the
> pressure is lower
> above the wing than below.  This difference in pressure results in an 
> upward
> force
> we call "lift", which is what holds up the airplane."  I'm paraphrasing 
> from
> memory,
> but that is as close as I can remember to an exact quote.
>
> Never mind that this "explanation" would imply that planes cannot fly 
> upside
> down,
> which obviously they can.