Re: [Phys-l] interaction

[Brian Whatcott <betwys1@sbcglobal.net>]

At 08:41 AM 8/5/2007, John D., you wrote:

> Observations:  Ball #1 hits ball #2 and comes to rest.  Balls
> #2, #3, and #4 remain nearly at rest, nearly at their original
> positions.  Ball #5 goes flying.
>
> Analysis:  To a good approximation:
>  -- All of the rightward momentum initially in ball #1 is transferred
>   out of ball #1, which is a big net loss of rightward momentum for
>   that ball.
>  -- Rightward momentum flows /through/ balls #2, #3, and #4 with no
>   net gain or loss of momentum for those balls.
>  -- Rightward momentum flows into ball #5, which is a big net gain of
>   rightward momentum for that ball.
>
>   Note that the direction of flow is distinct from the direction of
>   momentum.  A /push/ is a rightward flow of rightward momentum, or
>   (equivalently) a leftward flow of leftward momentum.  In contrast,
>   a /pull/ would be a rightward flow of leftward momentum, or a
>   leftward flow of rightward momentum.


Hmmmm....I prefer to use the transmission line model.
A mechanical transmission line, whether it is a row of balls, or a metal rod
or whatever, transmits an impulse in a reasonably well understood way:
sometimes as a compression, rarification, shear, or twist wave.

In this way, I don't need to deal with the dynamic physical descriptions of
abstract qualities like transfer of momentum.      This is not to deny
I can handle phrases like the flow of [heat] energy, where the underlying
physical mechanism is tedious or quasi-statistical. I can, and I do.



Brian Whatcott    Altus OK    Eureka!