Re: [Phys-L] feeler-dealer, third law, et cetera

[jbellina <inquirybellina@comcast.net>]

Seems to me there is logical error in your analysis.  The claim in Newton's third is not about "net force" but about individual interactions between objects.  Net force is a mathematical construct and thus does not necessarily have physical sense in the way that individual ones do.  It seems to me to be a false generalization to say that because individual forces follow Newton's third, that all constructed forces must also.

joe

Joseph J. Bellina, Jr. Ph.D.
Emeritus Professor of Physics
Co-Director
Northern Indiana Science, Mathematics, and Engineering Collaborative
574-276-8294
inquirybellina@comcast.net


On Dec 12, 2013, at 7:12 AM, John Denker wrote:

> > Net force isnt *A* force it is a sum of forces.
> > An account balance is neither a debt nor a deposit.
>
> If we adopt that approach, it means force is not a vector.
>
> I say that because according to the definition of vector,
> the sum of two vectors must be *A* vector.  This is called
> /closure/.  This requirement is so fundamental that it 
> sometimes goes without saying when people are listing the 
> vector-space axioms:
>  http://en.wikipedia.org/wiki/Vector_space#Definition