Re: [Phys-l] Fields and touch?

["John Clement" <clement@hal-pc.org>]

This webpage is not very accurate.  It talks about a layer of repulsion
between the atoms.  In reality there is bonding between the nearby atoms.  I
do not know the type of bonding when 2 things touch, but I suspect it may be
Van der Waals forces.

As I pointed out in a previous message the atoms do not repel each other
unless they interpenetrate in some fashion (classically).  While it is true
that theoretically electrons can not touch because of the repulsion, and of
course the nuclei do not touch each other, the surfaces of the atoms
(defined in some mathematical fashion) can touch and actually penetrate each
other.  When atoms bond covalently the electrons are exchanged and the atoms
are actually closer together than if they were not bonded.

The very term layer of repulsion is very misleading and will tend to produce
misconceptions.  It makes the students think of forces as being like
objects, and brings up the image of a force field as being a physical
object.  One must always talk about forces as being interactions between two
physical objects and identify what each object is doing to the other.  The
SF force field is a cute idea, but does not exist.

One can say that atoms can not touch because they don't have surfaces, but
that is not clearly brought out.  So students will still picture atoms (if
they do picture them) as being little hard round balls with a layer of stuff
in between repelling them.  In other words they will picture the plum
pudding model.

John M. Clement
Houston, TX

> -----Original Message-----
> From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-
> bounces@carnot.physics.buffalo.edu] On Behalf Of sridhar chitta
> Sent: Tuesday, February 23, 2010 6:15 AM
> To: Forum for Physics Educators
> Subject: Re: [Phys-l] Fields and touch?
>
> Please visit the following webpage
> http://www.worsleyschool.net/science/files/touch/touch.html
> I hope this answers your question.
>
> - Sridhar chitta
> On Tue, Feb 23, 2010 at 7:14 AM, Tony <physixdude@comcast.net> wrote:
>
> > When my hand rests on the table, do I touch the table? ...Or do the
> > electric
> > fields between my hand and table leave a gap between the to objects?
> Maybe
> > it comes down to how "touch" is defined?
> >
> > -Tony
> >
> > --
> > Tony Wayne
> > Albemarle High School
> > Physics Teacher
> > Science Department Chair
> > twayne@k12albemarle.org
> > http://www.mrwaynesclass.com
> > -
> > Those who can do.
> > Those who understand, teach.
> >
> >
> >
> > _______________________________________________
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>
>
>
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>
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