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Re: Newton's 3rd Law

Lisa Morris ( wrote:

Hi all, I've just resubscribed to this list after a relatively long absence
and have no idea what the current discussions are, but thought I would
throw a question to the group that was recently thrown at me and has
initiated a lot of discussion.

The question:

Are there limitations to Newton's Third Law and, if so, what are they?

I'm anxious to hear what you all think.

Lisa K. Morris
Instructional Lab Supervisor
Department of Physics
Washington State University
Pullman, WA 99164-2814
(509) 335-8298
(509) 335-7816 FAX

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 |