Re: F=m*a, was Thermodynamics

[Jim Green <JMGreen@SISNA.COM>]

> If it is permissible in thermodynamics to say that gas molecules *could*
> do something (collect in one corner of a container) but are instead
> observed to do something else in every case (distribute themselves
> throughout the volume of a container) why can we not say that an object
> *could* have any acceleration but instead is always observed to have an
> acceleration which could be predicted by the equation a=Fnet/m?

1) Because, if one is talking about a single object which follows the
approximate law F=ma, there are no statistics involved -- at least not
classically - whereas in your thermo example there are.  The difference you
are looking for lies in the stats.

2) Because it is not always true that F=ma
   -- unless one does a bit of gymnastics in defining F, m, and a.


Jim Green
mailto:JMGreen@sisna.com
http://users.sisna.com/jmgreen