Re: [Phys-l] God as an explanation (WAS: Darwinism underattack?andthephysicsclassroom)

[Hugh Haskell <hhaskell@mindspring.com>]

At 17:28  -0500 8/1/08, David Whitbeck wrote:
> Without calculus students can't even explore the relationship 
> between momentum and force.  I certainly don't advocate any such 
> derivation or even mentioning it in an algebra based course.  And in 
> a calculus based course, stating the connection and illustrating it 
> would be more appropriate than trying to derive it.  Anyway unless 
> it's very short and sweet, imho derivations don't belong in 
> introductory physics.  Students at that level don't really have a 
> good internal ranking of basic eqns and concepts vs derived results.
I think I disagree with most of this paragraph. Students can explore 
the relationship between momentum and force without using calculus. I 
taught my introductory HS students for several years, starting with 
momentum, and using that to "derive" (quotes meaning that the 
derivation was mostly non-rigorous) the idea of force as being what 
causes momentum to change. In fact, we started with momentum 
conservation as an empirically-discovered principle, and from that 
beginning found all three of Newton's Laws. This can be done 
rigorously, using calculus, but calculus isn't necessary to give the 
students an appreciation of how the two ideas are related. This was 
in an algebra-based course without even using trig. All the physics 
was one-dimensional, so we didn't have to worry about vectors or the 
complications they entail.

And I believe that derivations that the students can follow are 
useful in an intro course, provided they are used sparingly, and done 
for the purpose of showing them that the results are derivable and 
are not something that just came from whole cloth (except, of course, 
where they *do* come from whole cloth--i.e., experiment).

I never asked them to derive any equation that involved more than 
just simple algebraic manipulation, but they always got to the point 
where they could take the work on to problem solving, knowing that it 
had a firm foundation, and wasn't just another formula thrown at them 
by their teacher.

The object of an introductory science course is to get them to 
understand the old saw that "science is no more a collection of facts 
than a pile of stones is a house." If they don't know that what they 
are doing when they are solving a problem is based on 
well-established fundamental principles (where they really are), then 
they will never understand the above metaphor. It isn't necessary 
that they be able to understand the chain of reasoning or be able to 
reproduce the development at this early stage--it is enough that they 
know it exists, and that they can understand it with further study if 
they feel the need. Unless they understand that, they will have no 
idea of what science is about, and we will have wasted our time with 
them.

Hugh
--

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Hugh Haskell
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<mailto:hhaskell@mindspring.com>

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