Re: [Phys-L] A Couple of Instances Where "Power" Is Not Power

["John Clement" <clement@hal-pc.org>]

If the FCI is little more than word games how come it correlates almost
perfectly with the FMCE which uses very exact physical examples.  The FMCE
often presents the answers as graphs rather than as words.  In reality the
words are important to the "understanding".  Being able to use words
correctly in a given context are one measure of understanding, but by no
means the only measure.  The two tests are so different that they do not
look like they are testing the same things, but a simple correlation study
shows that whatever they are measuring seems to be the same.  The FMCE would
seem to have a lot less dependence on vocabulary.

So what about the NTN3 questions?  It really doesn't matter whether the term
is force, impulse, or momentum transferred.  The answer is always equal.
This is an alien idea to students.  They think that the truck does more to
the car than the car to the truck, no matter what you call it.  You can give
it is symbols or words and you will see the same result with respect to
student answers.

Sure the FCI is not the only measure.  The Lawson test is another measure,
and problem solving can also measure other factors as long as it is done
carefully.  Until you actually give the FCI and then look at other measures,
you can not appreciate how powerful it seems to be.  Mazur documents how
targeting the FCI improved the problem solving of the lower level students
in his class.  But just targeting the FCI alone does not produce appreciable
gain on Lawson, so you must do other things as well.

Until we have better evaluations that can be used in class the FCI/FMCE
remain the most important ones.  Can anyone come up with a better one???  If
so PUBLISH it and see if it does a better job.  Belittling the only ones we
can use for comparison is not helpful.  I always suggest using it and see if
you can produce higher scores.  If you have never done this, you do not know
how it actually works.  Remember teaching is an experimental science, not a
theoretical one.

John M. Clement
Houston, TX

> Many of the FCI questions are IMHO little more than word 
> games, designed to trick students into answering in terms of 
> vernacular force (as in causation) rather than mechanical 
> force (as in Newton's laws).  The "right" answer is obvious 
> to physicists, because we spend all day in physics context.
> However, students could reasonably read the question in 
> another context.  I'm not even willing to call the typical 
> student answers wrong, because the FCI is so grossly context- 
> dependent.  It focuses on the /word/ force rather than any 
> operational consequences of the concept.  So really it should 
> be called FVI:  Force Vocabulary Inventory.