Re: third law forces cancel?

[Larry Smith <larry.smith@SNOW.EDU>]

At 2:05 PM -0400 10/11/04, John Denker wrote:
> There should be no difference mathematically or pedagogically.
> I would hope the students would realize that
>   k = -j  <==>  k + j = 0
> is a tautology.  They normally learn that in 4th grade if not
> sooner.

Yes, I think they did learn in the 4th grade that your double implication
is a tautology.  I don't think that _necessarily_ makes the two statements
equally advantageous pedagogically (and maybe that can only be determined
experimentally by the PER people, but it isn't a big enough deal for me to
pursue further here).

Larry