Re: Thermodynamics

[brian whatcott <inet@INTELLISYS.NET>]

At 21:49 8/29/01 -0400, you wrote:

> A few days ago I posted a request for comments regarding some ideas I heard
> in a thermo class.
>
> Related to that, could I solicit some more comments on this one:
>
> "There is no reason to expect that an object will have any one particular
> acceleration given a certain force.  When the acceleration of the object is
> measured, however, we find that it obeys a law of the form a = F/m."
>
> Thanks
>
> Justin Parke

It is a very strange thing to consider the sudden appearance
of something like an Earth mass near a star.
Supposing there is some motivating attraction which can act at a
distance, one imagines that there is the necessity for a message
to travel between both bodies, in order to modulate the force so
as to produce an identical acceleration, no matter what the mass
of the appearing body.

This has all the comedy value of Bugs Bunny hanging over a precipice
until he looks down.

 A more comfortable model, in some ways, is to suppose that each
mass interacts with the surrounding space in a way one calls a field
effect.

A new body can immediately respond to the gradient of a gravity well,
one imagines, by rolling down it, or balancing the fatal attraction
with its propensity for continuing in the same direction in which it
was heading, if tangential to the star.

When unsure of a theoretical underpinning, it is always
open to everybody to speak in terms of observables, and their relations
(though there may be unspoken assumptions, such as no suddenly
appearing masses, which don't present themselves every day, certainly...)

In the case you cite, all the terms are manufactured, to some extent
rather than directly observed:
we need to define
what is mass?
what is acceleration?
what is force?
...and this is the business of physics.

Brian W


brian whatcott <inet@intellisys.net>  Altus OK
                Eureka!