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Re: [Phys-l] Student Misconceptions



On 09/29/2011 07:45 AM, Joseph Bellina wrote:
Once again, I would not classify any of these as mis or pre
conceptions. They are rather misinformation.

OK, several people have recommended this sort of distinction.
Similarly, several people have recommended classifying
???conceptions based on whether they were acquired in school
or elsewhere.

That seems kinda plausible, and I'm not saying I disagree,
but I don't fully understand ... so I request more detail,
if possible.

In particular, the equally plausible alternative view is that
what really matters (to first order) is how deeply held the
???conception is. The origin of the ???conception is not
/directly/ relevant ... although it may be /indirectly/
relevant insofar as it may help predict how deeply held the
???conception is.

To second order (and more importantly) I reckon we have to
take these things on a case-by-case basis. Each incorrect
conception (like each correct conception) is tied to various
other things that the person "knows". To refute the ???conception
requires untying it.
a) The sink-or-swim approach is to tell the person "This
???conception is wrong and you need to untie it from
everything else, whatever that may be. Figure it out."
b) The more selective approach is to find out where the person
is coming from, in detail, and then to help them untie the
???conception from the /specific/ ideas that are supporting
it.

In my experience, approach (b) sometimes involves recognizing
that the ???conception may contain a germ of truth.

The first law of motion may be the perfect example. I might
say: In situations where friction is overwhelmingly important,
objects *do* tend to come to rest. That's fine. You can keep
that idea. However, you must learn to distinguish it from
situations where friction is not so important. In this class
we will start by considering situations where friction is
completely negligible, and then ......

On 09/29/2011 10:08 AM, Philip Keller wrote:
The point is that most of my students believe that heavier objects
fall faster even after they have "learned" otherwise.

Well, actually they generally do fall faster. They don't fall
as /much/ faster as students think they do, so there's still a
misconception here that we need to deal with ... but IMHO we
ought not overstate the case.

As another example concerns the exceedingly prevalent ???conceptions
about the definition of "acceleration". I would argue that the
vernacular notions of acceleration and deceleration refer to the
/scalar/ acceleration, i.e. a change in speed. That is perfectly
reasonable and perfectly well defined, but must be recognized as
different from the /vector/ acceleration, i.e. a change in velocity.
For details, see
http://www.av8n.com/physics/acceleration.htm

To repeat: scalar acceleration and deceleration are not wrong,
just different from the vector acceleration.

At a more advanced level, I take a similar approach to the holy
wars about the definition of "heat". It seems to me that there
are at least four different technical definitions of "heat" in
common use (not to mention innumerable nontechnical and metaphorical
meanings). IMHO the best way forward is *not* to pick one of these
and argue that it is correct to the exclusion of the others, but
rather to bypass all of them and reformulate the whole subject in
terms of energy and entropy ... not "heat" at all.

==================

FWIW IMHO approach (a) is not wrong. A big part of critical
thinking -- and learning in general -- involves examining every
idea that comes along, turning it over in the mind, to see how
it connects with everything else that is known. This involves
checking for supporting evidence as well as conflicting evidence.
This applies to unlearning as well as regular learning.

Students need to learn this! I reckon the goal should be to get
everybody to the point where approach (a) is sufficient. Teaching
people how to learn and how to think should be the highest priority.

OTOH we must recognize that most people are not yet ready for
approach (a), in which case approach (b) will be more successful.
Alas approach (b) is vastly more of a burden on the teacher.

=======================

Anyway, returning to the original point: I leave it as a question:
Is it true that classifying the ???conceptions is only indirectly
important?
-- At one extreme, all that matters is how deeply held the
???conception is.
-- At the opposite extreme, it matters in detail how the
???conception is tied to other things that are "known".
-- So maybe the question is, what does the middle ground look
like? What am I actually going to do differently if I think
it is a preconception as opposed to a misconception?

Or is that the wrong question?