Re: Newton's 3rd Law

[Joseph Bellina <jbellina@saintmarys.edu>]

On Wed, 3 Apr 1996, Mike Thayer wrote:
Can you help me out with this?  It seems to me that the third law relates 
to hand on rod or rod on hand, or rod on box or box on rod, so I don't 
see how propogation time is an issue.

thanks

> I think the simplest answer to this question is a thought experiment.
>
> Suppose you have a long rod, one end of which is up against a box, the other
> end is free, e.g.:
>
>
>
>              _____________
>              |           |         _very_ long rod (longer than this)
>              |   box     |==========================================<--Force
>              |           |
> _____________|___________|____________
>
> You apply a force to one end of the rod.  Will the box move right away?
> Next question:  does this invalidate Newton's 3rd Law?
>
> :)
>
> Mike Thayer
> Laboratory for Astrophysics & Space Research
> The University of Chicago
> thayer@odysseus.uchicago.edu  |  http://astro.uchicago.edu/home/web/thayer/