Re: [Phys-l] question about Bernoulli

[John Mallinckrodt <ajm@csupomona.edu>]

On Nov 23, 2010, at 2:31 PM, LaMontagne, Bob wrote:

> Certainly the density is lower. But the gas is flowing through much faster, 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 a conceptual, 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