Re: Newton's 3rd Law

[jmclean@chem.ucsd.edu (James Mclean)]

Tom K. McCarthy says:
> What's wrong with the notion of action/reaction?  By using concrete 
> examples to help the student experience Newton's 3rd Law, it seems quite 
> natural to describe these as action/reaction, and, consequently, we find 
> that forces aways occur in pairs.

I think that the problem is in the everyday usage of those words.
If you are not using physics-speak, then you would probably say something
like: 
   action: I push the cart.
   reaction: The cart moves.

In terms of the 3rd law, the reaction should be that the cart pushes back
on me.  You *could* teach that there are 2 meanings for the word reaction,
the physics meaning and the everyday meaning.  But it's probably easier to
avoid the confusing nomenclature altogether.

-- 
--James McLean
jmclean@chem.ucsd.edu
post doc
UCSD