Re: [Phys-L] Conceptual Physics Course

[John Denker <jsd@av8n.com>]

On 05/14/2012 06:13 AM, R. W. Tarara wrote:

> 1) This is the most difficult course to teach, but arguably the most
> important.
>
> 2) Don't get carried away with your goals--pick two or three and
> concentrate on those. It will be difficult enough.
>
> 3) If you do (2) the challenge is to prioritize and choose the most
> appropriate goals, but that will be more or less a personal choice.
>
> 4) Using 'Themed' courses makes this easier.

Yes, having a _theme_ has definite advantages.  It (a) helps 
with the motivation, and (b) serves as a source of real-world 
non-BS examples to look at.

The obvious downside is that the theme generally requires a
lot of non-physics learning along with the physics.  This
does not bother me at all.  I'm not a physics bigot.  If the
other stuff is worth learning, let's go ahead and learn it.
Teaching physics half the time with good motivation and good
retention is waaay better than teaching physics 100% of the
time with poor motivation and minuscule retention.

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

On 05/19/2012 03:22 PM, Jeffrey Schnick wrote:
> My original question was  "... what do you do to convince a person in
> a lasting manner that the reciprocal of (1/x + 1/y) is not, in
> general, x+y?" 

> My new version is: What do you do to make it so that
> a person who has a tendency to replace 1/(1/x+1/y) with x+y gains the
> understanding and habits of mind that result in that person not
> replacing 1/(1/x+1/y) with x+y ?

Right.  The new version is incomparably more interesting and
more important than the first.

The original version asked about the superficial symptom, 
whereas the second version calls for treating the underlying 
disease.

> A scenario in which the people in the class discussed above developed
> habits of checking their work and making connections such that
> despite the poster child mistake never being addressed by the
> teacher, the mistake never reappears after the first month, does seem
> possible.

Right.

The converse is also relevant:  I reckon it is utterly 
impossible to take the direct approach, directly teaching 
students about the poster-child mistake and teaching them 
to avoid this specific mistake.  Here's why:  Avoiding the
poster-child mistake is a double-negative idea.  It's not 
constructive.  Even if the students learn what 1/(1/x+1/y) 
is not equal to, they still don't know what it *is* equal 
to.  Therefore this factoid is essentially useless ... and 
the students know it is useless, which is a powerful reason 
to not bother remembering it.

I would go even further and predict that even if the students 
learned some more constructive information about this formula, 
the information would still be near-impossible to remember, 
because memories are strengthened every time they are used, 
and this formula just doesn't get used often enough.

IMHO this is not an important formula ... and pretending it is 
important doesn't help.  Sure, you could make it seem useful 
by cooking up an assignment on the topic every week for 35
weeks, and you could make it seem important by saying it will
be worth 20% of the grade on the final exam.  Alas, however, 
the students would see this for what it is:  artificial 
usefulness and artificial importance.

Also this comes at a terrible price, because there are a
gazillion formulas of equal real importance, and you cannot
make them worth 20% apiece on the final exam.

Thirdly, even if you get them to remember this formula all 
year, they will forget it by the end of June, because they 
will no longer be getting reminders.  That means the whole 
enterprise will have been a waste of time and money.

====

The problem is, too many students arrive with the notion 
that they are "supposed" to learn, verbatim, the fact that
1/(1/x+1/y) is not equal to x+y.  Therefore the first
order of business must be to disabuse them of that notion.
Otherwise they will be doing the wrong thing.  What's worse, 
they will fail at doing it.

To repeat:  They will fail to remember what 1/(1/x+1/y)
is not equal to ... and even if they succeeded, it would
be the wrong thing to do.

In much the same way that a geodesic dome or a structural
truss is a lattice of nodes held together by struts, practical
knowledge is a lattice of facts held together by principles.
 -- You need the facts, and
 -- You need the principles.

Trying to get along by memorizing disconnected factoids (in
the absence of principles) is what I call the Rain Main 
approach.  Everything we know about human memory says this 
approach is guaranteed to fail.  Observation supports the 
theory:  We see this approach fail day after day, year after 
year ... e.g. when students take three years of high-school 
math and then arrive at college unable to do basic algebra
and not knowing what the word "perpendicular" means.

A near-synonym for "principles" is "concepts".  I just amazes
me to see books on "conceptual physics" that teach factoids
to the near-exclusion of concepts!

This thread got started by a question on how to organize a
conceptual physics course.  I have an idea, a vision that
expresses what I would like to see:

I imagine three piles of "visual aids" i.e. sight gags:

  In the first pile, there is a copy of the Call of Duty
  game, a yellow toy vehicle representing Cash Cab, and
  an SAT test booklet.

  In the second pile, there are some more games: checkers, 
  chess, go, Clue, Sid Meier's Civilization, some poker chips,
  and maybe a copy of the Moneyball book (or movie poster).

  In the third pile, there is a five-pound bag of flour, a 
  child's shoe, a cinder block, a cell phone, a balsa-wood 
  airplane, and a cardiac pacemaker.

Have you figured out the symbolism?  

  In the first pile are twitch games and trivia games.
  Little if any strategy required.

  In the second pile are games involving strategy and
  deduction.  These have much more intellectual heft 
  than the things in the first pile.

  In the third pile are representations of real things:
  Food, clothing, shelter, communications, transportation,
  medical care, et cetera.

Games are categorically different from real things, because
even if you win, it's still just a game.  Even in the very
very rare cases where you get paid to play the game, you do 
it for the enjoyment of spectators who already have food, 
clothing, shelter, leisure time, and disposable income.

And oh yes, I meant to put the SAT and the NCLB-mandated
standardized tests in the "trivia" pile.  Not only are they
merely games, they are pathetic trivia games, with less
intellectual heft than a game of checkers.  Students are 
trained that if you can't answer the question in 45 seconds, 
the question is not worth answering.  That's only slightly 
more intellectual than Cash Cab, which gives you 30 seconds.

In contrast, it takes more than 45 seconds to produce a
shoe (not to mention the materials that go into it).  It
takes more than 45 seconds to grow crops.  It takes more
than 45 seconds to convert a pile of cinder blocks into 
a habitable building.  It takes longer than 45 seconds 
to implant a pacemaker into somebody's chest.  All these 
things take time /and skill/.

I am fed up with physics in particular and school in general
being treated like a trivia game, involving little or no
strategy.

We know the students are capable of strategic thinking,
making a series of moves in pursuit of a distant goal.
We know this because we see it in the sports and games 
they play.  We need to change things so that henceforth
they apply the same level of sophistication in class.

At this point I wave around the shoe.  This is a child's
shoe.  Dear students:  Suppose you have a family some day.
The questions that will come up about how to take care
of your family will *not* be multiple-choice questions.
They will *not* be answerable in 45 seconds.  And you
will *not* get to skip the questions that seem hard.
This is not a trivia game.

At this point I wave around the airplane.  Do you recall
that guy, Sully Sullenberger, who landed his Airbus in
the Hudson River and got all the passengers out alive?
There is a lot of physics that went into building that
plane so it could take off at all, let alone fly fast
and efficiently.  There is also a lot of engineering
that went into making sure it would still fly after
losing both engines, and making sure it would float
long enough to get everybody out.  Last but not least,
the flight crew had trained for years to make sure they
knew what to do in an emergency.  The result was not
due to a miracle;  it was due to skillful engineering 
and skillful piloting.

At this point I wave around the cinder block.  Cinder
blocks can provide shelter, but they can also kill you.
Over the years, lots of people have been killed by badly-
designed buildings that collapse during an earthquake.
This is the Sullenberger story in reverse:  If you do 
the science and engineering wrong, people die.  This 
is not a trivia game.

Telling that story is the easy part of the job.  The
hard part is working all day every day for the rest of
the year, fighting to keep the trivia from creeping back 
in and to keep the plug-and-chug from creeping back in.