Re: [Phys-l] question about Bernoulli

[John Denker <jsd@av8n.com>]

On 11/23/2010 08:27 AM, LaMontagne, Bob wrote:

> the component of velocity of the molecules perpendicular to the
> pipe walls - was it reduced? 

Yes.

> and by what mechanism was it reduced?

Particle/particle collisions.

Each collision can be visualized in terms of points on a sphere
in six-dimensional phase space.  Ignoring the mass for simplicity, 
we have:
  v1x^2 + v1y^2 + v1z^2 + v2x^2 + v2y^2 + v2z^2 = E = constant

Each collision will cause the system to random-walk on the
sphere.  If every collision were one-dimensional (i.e. zero
impact parameter) we would not have a random walk, but since 
the impact parameters are random we do.  The energy will soon
be distributed over all the accessible states.