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Re: [Phys-l] Mass and Energy



This is where the retrieval problem becomes severe. As I recall it was
probably in a more general article and was an example of where a commonly
taught procedure can interfere with understanding. But I can not recall the
specific article. Being a science/math education research omnivore poses
problems.

However, it does make sense. Once you understand proportional reasoning,
you know what to do for simple conversions. You also compare the size of
the result with physical reality. These are steps that are not followed by
students when they learn a rote procedure. Factor label short circuits the
reasoning so it never develops. It is undeniably useful in some cases.

An example here is the conversion from cm to m. Students can parrot back
there are 100 cm per m. But notice that per hides the difficulties. They
need to be able to say that there are 100 cm for each m. This is
recommended by Arons. Then when asked how many cm there are they have a
better chance of getting it right. However the reverse conversion is the
problem. They will glibly tell me that 10 cm is 1000m. I always ask them
to compare what this means in terms of distance.

John M. Clement
Houston, TX


I may have missed this before but could you cite the research that you
refer to?

----------------------------------------------------------
Robert A. Cohen, Department of Physics, East Stroudsburg University
570.422.3428 rcohen@po-box.esu.edu http://www.esu.edu/~bbq

-----Original Message-----
From: John Clement
Sent: Friday, May 26, 2006 3:06 PM

Part of the problem is the introduction of factor/label
before students have learned what unit conversion means.
There is research evidence that factor/label prevents
understanding. It is also often not the most efficient way
of doing conversions, especially when only 1 step is required.
Factor label becomes just another incomprehensible procedure
for way too many students.

John M. Clement
Houston, TX
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