curve balls, airfoils, greenhouse effect

["Richard W. Tarara" <rtarara@saintmarys.edu>]

Quoting myself-- ;-)

> If I'm to abandon certain topics or certain explanations that I've gotten
> from supposedly reputable sources, I want to be damn sure those sources
> were wrong.   I suspect that for many of us it is harder to UNLEARN
> something than to learn it, and that is exactly what we're being asked to
> do by the 'authorities' on this list.  They may be correct, and I am
> convinced that all these phenomenon ARE more complicated than the simple
> text-book descriptions, but ultimately the acid-test is whether or not
> there is any pedagogical advantage to keeping a simple (even
> misrepresentative) description of a phenomenon.  To some that answer is
> clear, I'm still struggling with it. 

On overnight reflection, I suspect I will abandon the curve ball as an
intro topic (in fact haven't used this example in a couple of years).  It
is interesting (to me) that in doing a quick calculation in my head while
driving in this morning--using the Franklin Miller Bernoulli description--I
came up with 20 revs/s to give a .25 m deflection for a 40 m/s pitch
travelling 20 m.  Seems in good agreement with Paul's numbers for rpms of
real curve balls.

However, I won't abandon the greenhouse effect description since it does
seem to help students grasp the global greenhouse effect.  This is one of
the few topics that I can ask the question "EXPLAIN--" and NOT get
gibberish back from half the class.  It seems to me to be sufficient to
present the 'standard' explanation and then add that this effect is
_greatly_ enhanced in real greenhouses and cars by the lack of convenction
cooling.  That's not a LIE --IMO.

I'm not ready to give up Bernoulli on airfoils yet either.  Again,
calculations give reasonable numbers, and I really haven't heard or seen a
description that negates Bernoulli as a _major_ factor in LOW SPEED
airfoils--again such as those used with human-powered craft.  I also wonder
about ultra-lights.  To be sure, I've always raised the question of how can
airplanes fly upside-down with my classes and therefore get at attack
angle, conservation of momentum contributions.

HEAT--well I can't see any advantage for my classes in NOT talking about
heat as thermal energy.  We deal mostly with calorimetry ideas, and trying
to define Heat of Combustion, Heat of Fusion, Heat of Vaporization,
Specific Heat, Heat Engines, Heat Exchangers, etc., etc. with 'Heat' as a
verb and with 'Heat' not being a form of energy doesn't seem practical. 
I'll stay with the 90%+ of texts that don't agree with Jim.  Besides, even
in T#1 where I sort of see Jim's point, he ends up with (2 nouns = a verb)
syntactically and that doesn't sit right either.
 
I'll TRY to refrain from any more comments on these threads.   <ggggg>

Rick

*****************************************************
Richard W. Tarara                  
Department of Chemistry & Physics      
Saint Mary's College                    
Notre Dame, IN 46556 
219-284-4664 
rtarara@saintmarys.edu  
                  
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