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

[jbellina <inquirybellina@comcast.net>]

I'm sorry but this idea of an object being a collection of objects seems sophistry to me.  If we want our students to believe this stuff has real meaning for them, we need to keep it simple.  N3 applies to the interactions between real objects, they are individual force pairs.  Just because a force can be mathematically represented by a vector and the vectors can be added in there vector way does not make the sum a force in the same sense that the individual ones were.  So to keep it simple N3 applies to pairs of objects interacting with each other.  It does not apply to the mathematical artifice we call the net force.
Seems pretty straight forward to me.

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 11:18 AM, Jeffrey Schnick wrote:

>  If the force on A in question is the sum of forces exerted by each of several different objects then the agent of the force is the compound object (B) that is the collection of those other objects, and the sum of the individual Newton's third law partner simple forces is the  Newton's third law partner force being exerted by A on B.