Re: Newton's 3rd Law (signed)

[msantos@etse.urv.es]

Forwarded message:
> From server@atlantis.cc.uwf.edu Wed Jun 12 18:00:19 1996
> Message-Id: <199606121647.RAA17848@etse.urv.es>
> Date: Wed, 12 Jun 1996 17:47:24 +0100 (GMT+0100)
> Reply-To: phys-l@atlantis.cc.uwf.edu
> Sender: owner-phys-l@atlantis.cc.uwf.edu
> Precedence: bulk
> From: msantos@ETSE.URV.ES
> To: phys-l@atlantis.cc.uwf.edu
> Subject: Re: Newton's 3rd Law
> In-Reply-To: <Pine.OSF.3.91.960611193229.6122D-100000@thurman.tenet.edu> from "James Andrew Jones" at Jun 11, 96 07:35:55 pm
> MIME-Version: 1.0
> Content-Type: text/plain; charset=US-ASCII
> Content-Transfer-Encoding: 7bit
> X-Mailer: ELM [version 2.4 PL24]
> X-Listprocessor-Version: 7.2 -- ListProcessor by CREN

I forgot to sign my previous mail.
msantos@etse.urv.es
spain
> > I have always had trouble with students misunderstanding Newton's third law.
> >
> > I have lately come to realize that they don't know what a force is.  
>
> Well I'm not sure if there is a precise meaning of force, but we
> may see its properties:it behaves like a vector and its effect
> is to change the movement (in speed and/or direction).May be they try
> to identify a 'force' in the same way as one identifies a particle.
>    Related with this, I would like to know if someone from the list
> has experienced with:
>             .-Starting mechanics without kinematics, but definig
>             change of movement (as the effect of interacction of
>             particle and in the sense previously given)
>             .-Then introducing the term force as a suitable way
>             of describinf this change and showing them that it
>             behaves like a vector (undr composition)
>             .-The quantitative law would be Newton's 2nd and 3rd.
> As a result, the law of inertia would be derived from the 2nd law.
> I thing that when working there would be no difference.
>
> Anyone agrees? desperate? 
>
> Are Newton's axioms realy all independent? I have never seen nothing
> about this (does this signal something?), but I've some doubts.
>
> > Their only experience is the "effect" of forces.  Since I have approached 
> > Newton's 3rd from the this viewpoint they seem to understand it better.
> >
> > When I start Newton's third, I stress that what they observe is NOT the 
> > two equal forces but the effect of those forces.  
> >
> >
> > Andy Jones
> > Physics Teacher
> > 1600 Loop 256
> > Palestine Texas 75801
> > andjones@tenet.edu