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

[Jeffrey Schnick <JSchnick@Anselm.Edu>]

It depends on what you mean by an object.  If for instance, in the case of two charged particles, you consider the particles to be the objects, then false.  But if you consider the objects, for instance, to be one particle and the field of the other, then true.  Force is momentum flow rate.  At the interface between the field and the particle, momentum is flowing from one to another.  The flow rate is equal to the rate that one is gaining momentum and to the rate at which the other is losing momentum.  Momentum is conserved locally.


> -----Original Message-----
> From: Phys-l [mailto:phys-l-bounces@phys-l.org] On Behalf Of John Denker
> Sent: Wednesday, December 11, 2013 5:01 PM
> To: Phys-L@Phys-L.org
> Subject: Re: [Phys-L] feeler-dealer, third law, et cetera
>
> True or false:  If an object is subject to a force F, some  other object must be
> subject to a force -F, simultaneously.
>
>  Assume short distances and long times, so we don't need to  fuss over the
> meaning simultaneity in special relativity.
>
> True of false:  The pairing of F with -F is absolutely required  by third law of
> motion.
>
> Please do NOT spend more than a few minutes thinking about this.  I will post
> my answers soon.
>
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