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-----Original Message-----
From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-
bounces@carnot.physics.buffalo.edu] On Behalf Of John Mallinckrodt
Sent: Tuesday, November 23, 2010 6:02 PM
To: Forum for Physics Educators
Subject: Re: [Phys-l] question about Bernoulli
On Nov 23, 2010, at 2:31 PM, LaMontagne, Bob wrote:
Certainly the density is lower. But the gas is flowing through muchfaster, so more molecules in a given time will pass a given area of
wall and exert more pressure (hit the wall more often) than a
stationary gas of the same reduced density.
I think you need to think that one through a little better. If twice
as many molecules pass a region in a given time, they each spend half
as much time there.
So which effect dominates?
There isn't any competition. Lower density and a barotropic equation
of state (due to the adiabatic assumption) => lower pressure, period.
I think the spirit in which Bill asked the question requires aconceptual, non-mathematical answer.
You don't like "Less squeezing => less pressure"?
I don't think I can do any better, but maybe someone else will.
John Mallinckrodt
Cal Poly Pomona
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