Re: momentum flow

["John S. Denker" <jsd@AV8N.COM>]

On 11/17/2003 07:59 PM, Herbert H Gottlieb wrote:
> I have had a bit of
> difficulty with your term "momentum flow"
>
> Is it similar to momentum transfer between a moving
> object and stationery objects that collide
> on the lab table??

It would have been impossible for a stationary object
to collide with a stationary table.  But I see Herb
is talking about _statonery_ objects, which can be
bounced against the table, no problem.  Erasers work
particularly nicely. :-)

Is steady momentum-flow similar to a collision?
Sure, conceptually almost identical.  The key
concept is:

  Force = momentum per unit time.

A typical collision involves a large amount of force
for a short amount of time, transferring a bounded
total amount of momentum.  But what's true of rapidly
changing forces is true for steady forces also:

  Force = momentum per unit time.

Saying object A pushes against object B is absolutely
synonymous with saying momentum is flowing across the
A/B boundary.  If A and B are objects in the conventional
sense, the converse holds also.

For _regions_ X and Y (including e.g. X=railcard and
Y=raincloud) it is possible to transport momentum
across the X/Y boundary without any force on the
boundary, just by free flow of momentum-bearing
stuff across the boundary.

For details see
  "Conservative Flow and the Continuity of World Lines"
  http://www.av8n.com/physics/conservative-flow.htm

  "A non-sneaky derivation of Euler's Equation"
  http://www.av8n.com/physics/euler-flow.htm