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Re: F before ma?



At 11:48 AM 10/16/00 -0700, bc with neck stuck out wrote:

one atm. applies force to an adjacent atm,
which then applies force to the next, etc.

On first reading, I thought atm. stood for atmosphere, in accordance with
the dictionary. On second reading I assume atm. is short for atom. I'm
not sure what is the advantage of a three-letter abbreviation for a
four-letter word.

It is done by mutual repulsion of electrons

It's a little more complicated than that, because the charge of the
electrons is almost exactly balanced by the charge of the nuclei.

(and Pauli exclusion if at relativistic speed?)

Pauli exclusion is important at all speeds. Relativity adds nothing to the
exclusion principle.

Pauli exclusion plus electrostatics is a good first approximation to the
physics of atomic collisions under ordinary conditions (e.g. STP).

this transmission is < C.

I would have said <= c.

Since the atm. (even the nucleus) has extent,
can the A and the F be simultaneous.

Yes. Why not?

The force doesn't happen everywhere at the same time, but the acceleration
doesn't happen everywhere at the same time either. This is easier to
imagine and/or observe for large objects; take a slinky for example.
Force here means acceleration here at the same time; a little later force
there means acceleration there at the same (later) time.

Perhaps, for the portion of the atm. that is
being "pushed", it's instantaneous -- over what resolution?

If you have a system of size L then electromagnetic forces are
instantaneous when your time resolution is on the order of L/c or longer.

(could Heisenberg help us here? maybe the resolution demanded is with in the
uncertainty, and, therefore, one can not show it's simultaneous or not?)

The uncertainty principle neither answers the questions being asked here,
nor impedes the answering of such questions.

(does special relativity "break down" at distances < say 10^-13 cm?)

There's no experimental or theoretical reason to believe it breaks down,
and abundant evidence that it does not break down. High-energy experiments
probe much smaller distances every day; violations of SR would be noticed.