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Re: [Phys-l] "Unlearning"



Regarding this comment:
To me, there is a vast difference between building a foundation for a future
physicist and introducing the broader population to the ideas of physics

Here Here!!

Both sets of students start with learning the scientific method - a cycle of model-making, model-testing, and model-"tweaking", that of necessity shows the models are imperfect and will continually improve. The average algebra-based physics student (non-major) encounters numbers everywhere all the time that have no written, explicit error associated with them (Kills 99.999% of all germs on contact; 0 grams Sodium, g = 9.81). I think it is critical for them to understand that these numbers also have uncertainty associated with them, even if it is not stated.

I make the Engineering Physics (calculus-based) students approximate the error in all experimental data and results, using Standard Error of the Mean, and usually include a confidence factor for a Gaussian distribution. They can handle it, and understand what it means. Error can be, and should be, predicted accurately.

(In case anyone cares, I teach the lecture on the pendulum starting from analysis of forces, and show explicitly that the model is only like a simple harmonic oscillator in the small angle limit - for both calculus-based and algebra-based students. I also have the students build a chart, as a class, to determine how far off the approximation is, for different values of theta - it isn't that hard, and it shows the limits of the model and its range of validity.)

Thanks, Mike, for your insight.

- Ann R.

From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-
bounces@carnot.physics.buffalo.edu] On Behalf Of Michael Meyer
Sent: Friday, September 10, 2010 11:30 AM
To: Forum for Physics Educators
Subject: Re: [Phys-l] "Unlearning"

"My examples about atoms filling their shells ,and
I think (and I'm interested to know if anyone
thinks I am wrong on this one), that refraction
is like a marching band? are rather different ,
as they are 'models' that are not useful
approximations but conceptually quite unlike the
target scientific thinking. - Keith"

The bigger question I don't think this discussion has addressed is that most
secondary physics students won't major in physics. (Or better still, most
secondary students won't ever take another course in physics!) I agree
completely that we need to put greater emphasis on the fact that we ARE
teaching imperfect models and analogies. BUT, I would say that many of these
things are taught as they are because a majority of students will never have
to "unlearn" the models taught in high school or even many introductory
college physics classes.

I'm not sure it's reasonable to adopt/require more complex models/analogies
when a majority of students will not have to "unlearn" simpler ones. I would
consider Keith's "marching band" and "filled shell" examples sufficient and
graspable as an explanation of refraction and simple chemistry for a vast
majority of the population. I won't defend significant figures, but will say
that for math-challenged students, "real" error analysis dramatically
compounds the mathematical difficulties (and fear!) students already have with
physics and physical science. For many students at the secondary level, a
simple conceptual understanding IS the "target scientific thinking."

To me, there is a vast difference between building a foundation for a future
physicist and introducing the broader population to the ideas of physics, and
most secondary schools necessarily focus on the broader population. That's
why physics majors have to "unlearn."

Mike Meyer
Senior Lecturer
Michigan Technlogical University
mrmeyer@mtu.edu