Re: is free-fall an inertial frame?

[Bob Sciamanda <trebor@VELOCITY.NET>]

Hi Stefan,
1) Newtonian response:
When Isaac gave us F=ma he was proposing that we could find an inertial
frame AND a set of force laws which would allow us to make sense out of
observed accelerations through the paradigm F=ma.  He
(successfully)applied this to the (then known) solar system by invoking
the universal gravitational force among all masses.
In this paradigm, an object in free fall at the earth's surface is
impelled by the gravitational force of the earth.  In searching for an
inertial frame, this force must be taken into account.

2) GR response:
You are entirely correct;  there is no "real" gravitational force;  only
"real" forces must be removed to experience force free motion. (But then
things are not so simple as in the F=ma paradigm.)

Bob

Bob Sciamanda (W3NLV)
Physics, Edinboro Univ of PA (em)
trebor@velocity.net
http://www.velocity.net/~trebor

"All such expressions as SQR(-1), SQR(-2), etc., are consequently
impossible or imaginary numbers, since they represent roots of negative
quantities; and of such numbers we may truly assert that they are neither
nothing, nor greater than nothing, nor less than nothing, which
necessarily constitutes them imaginary or impossible." Euler, in
"Algebra", 1770.

----- Original Message -----
From: Stefan Jeglinski <jeglin@4PI.COM>
To: <PHYS-L@lists.nau.edu>
Sent: Tuesday, August 17, 1999 1:07 AM
Subject: is free-fall an inertial frame?


> A question that's been bugging me for a while...
>
> I argue yes for the following reasons, and then pose the $10,000
question.
> 1. Newton's 1st Law is essentially a means of defining an inertial
> frame. It has a number of various wordings, similar to "any object at
> rest tends to stay at rest, and any object in motion tends to stay in
> that motion (straight line assumed), unless acted on by an outside
> force."
> . . .
> Stefan Jeglinski