Re: [Phys-L] force-pair question

[Richard Heckathorn <geepaw@wowway.com>]

Greetings, in the 70s I put the following above my chalkboard in my classroom. 

"How do I know why it is so?

And yes, there were cases when we never did find an answer. But that's the world in which we live.

Dick

Have a Great Day

Website rheckathorn.weebly.com



> On Jan 6, 2015, at 7:09 AM, Anthony Lapinski <Anthony_Lapinski@pds.org> wrote:
>
> My physics teacher in college remarked that "physics explains how, not
> why."
> I've always remembered this. Kids often want to know why things happen
> in the real world. We have physics "laws" which give answers and make
> predictions. But hey, nobody knows why the universe exists!
>
>
>
> Phys-L@Phys-L.org writes:
> > The problem lies with the word "why."  We do not know why.  We just know,
> > as
> > you point out, that this is one of the properties of forces in the
> > universe. 
> > We know how forces behave, not the reason they behave as they do.
> >
> >
> > > In other words, what evidence do we have that  Newton's 3rd law is
> > valid?
> > > I would say that this scientific generalization is "supported by
> > numerous
> > > experimental data."
> > >
> > > Ludwik Kowalski (see Wikipedia)
> > >
> > > =======================================
> > >
> > >
> > > > On Jan 6, 2015, at 12:40 AM, John Denker wrote:
> > > >
> > > > Hi Folks --
> > > >
> > > > A while back I came across the following question:
> > > > "Why do forces always occur in pairs?"
> > > >
> > > > That question comes from a CONCEPT CHECK in Hewitt chapter 7,
> > > > but I ask the following questions more generally:
> > > >
> > > > *) Have you ever asked that question on a homework assignment
> > > > or quiz?  If so:
> > > >  -- What is the official correct answer?
> > > >  -- What are the top one or two incorrect answers?
> > > >
> > > > *) Let's assume that "some" students read the book.  What
> > > > do they do when they come to this question?  Have any of
> > > > them ever asked you about it?
> > > >
> > > > *) If this question has never come up, why not?
> > > >
> > > > --------
> > > >
> > > > These are genuine non-rhetorical questions.  I am quite sure
> > > > I don't know why forces occur in pairs.  Probably I don't
> > > > understand the question, although all the words seem simple
> > > > enough.
> > > >
> > > > I tried googling, but the only answers I could find were
> > > > infantile or circular or both.  Paraphrasing slightly, the
> > > > leading contenders were:
> > > > -- Because forces always occur in pairs.
> > > > -- Because God said so.
> > > > -- Because Newton said so.
> > > > -- Because Hewitt said so.
> > > >
> > > > Are we really teaching students to give answers like that?
> > > > If this is what "conceptual physics" means, may God bless
> > > > it and keep it, far away from me.
> > > >
> > > > As for me, the only way I can imagine responding to the
> > > > question would have to be considered a non-answer, and
> > > > even so it is more complicated than anything one could
> > > > reasonably expect from a high-school student.
> > > >
> > > > So what's the deal?  Was Hewitt asking a trick question?
> > > > Or is there an actual answer?
> > > >
> > > > _______________________________________________
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> > >
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> >
> >
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