Re: [Phys-l] Any teaching tips

[John Denker <jsd@av8n.com>]

On 01/27/2011 11:57 AM, Philip Keller wrote:

> It is possilble that the ability to identify given information is a 
> reading problem.  You may want to coach your students to recognize 
> certain code words:
>
> "at rest" -- Vi = 0 m/s "to a stop"  -- Vf = 0 "at its peak"  -- Vy =
> 0 "dropped" ---  "Vy = 0  unless it was dropped from a moving
> object...

Yes, this is a good helpful comment.

What is here called "reading" is pretty much what I previously called
"algebra".  Perhaps an even better term would be "story problem" 
decoding skills.  A decent "Algebra I" course would include lots of
story problems, but the algebra teacher may have punted on this.

How many times have you heard a student say "I hope we don't have
to do story problems.  Ewwwww."  My response is to say that in the
real world, everything is a story problem.  If you ever want to
live in the real world, you'd better get used to story problems.

The constructive "tip" here is to check for story problem skills
*separately* from physics knowledge.  There are tons of story
problems available that don't require any physics, or perhaps
nothing more than 2nd-grade-level physics.  If the students have
trouble with those, you know you have to fix that before you
start worrying about the physics concepts.

> On 01/27/2011 11:18 AM, FOUAD AJAMI wrote:
> > For constant acceleration, tell students to place the 5 variables: 
> > vo(initial velocity), vf (final velocity) a (acceleration) s 
> > (distance) and t (time) in a table. Let them read the problem and 
> > extract from the wording three numbers for any three of the 
> > variables, leaving two blanks (unknowns). Search among the usual 
> > equations of kinematics - normally shown in any book - for the two 
> > most appropriate equations.

Wow.

As Rick T. and others have pointed out, that approach is notorious
for causing problems for the students in the long run ... and even
in the short run.  That approach is optimized for solving a narrow
class of "textbook" problems and cannot be extended to real-world
problems.  Forsooth, it cannot even be extended to the second
semester of introductory physics.  This is the sort of thing that
Philip K. called "robot training" ... except that from a robotics
point of view, it's not even a reliable or efficient algorithm.

I put this in the same category as counting on your fingers with
no notion of place value.  It is a phenomenally limited low-power
approach.

Way back on 6 Mar 2003 11:09:48 Joseph Bellina wrote:

> I'm reminded of a tale a friend of mine told me.  After graduating from
> college and ROTC he chose to go to the Army electronics school.  As a
> pretest he was asked what are the three most important laws of
> electronics.  Well he thought about that a while and chose j=sigma* rho,
> and Kirchoffs laws.  As it happened what they expected was
> V=IR, I = V/R and R = V/I

That story really stuck with me.

My point is that we want the students to get -- rapidly -- to the 
point where they see all three versions of Ohm's law as one equation.
By knowing one form of the equation explicitly and /understanding/ 
it, they know the other forms implicitly.

Continuing down that road, we want students to have thousands of
equations at their fingertips, not because they memorized a list
of thousands of equations, but because they understand a few
concepts _and the relationships between them_, such that they
/implicitly/ understand thousands of permutations and combinations
of the ideas and the equations.  The idea of solving problems
by searching a finite list of equations is like trying to play
chess by enumerating all possible states of the game-board.
It's just a terrible algorithm.  It might kinda sorta work in
selected special cases, but it doesn't work in general.

On 01/27/2011 11:46 AM, Dr. Richard Tarara wrote:
> > Conceptual quizzes, IMO, need to be a 
> > part of any physics course--probably clear on up to Quantum!

Indeed!

> > In my mind, any 'problem solving' courses--usually our Algebra based and 
> > Calculus based courses--need dual emphasis on both problem solving and 
> > conceptual understanding.

Dual emphasis is the key ... at all levels, from 3rd grade
through quantum and beyond, including cutting-edge research.

The equations tell you whether the concept is right.  The
concept tells you what equations you need to construct.