Re: [Phys-l] teaching physics conceptually

[John Denker <jsd@av8n.com>]

On 02/12/2011 01:55 PM, Kirsten Manning wrote:

> For my graduate class at UVa, I am working on an assignment that I
> will use with my high school students.  This assignment increases the
> amount of questions in tests and homework sets that are both
> qualitative and conceptual in nature .  I’ve always tried to
> incorporate some conceptual aspects to my labs, homework, and test
> questions, but I struggle with it in several areas.  Obviously, “plug
> and chug” is easier to teach than the conceptual nature of physics.
> Show the students the pattern to a formula and they can find numbers
> to plug into an equation with very little effort.   Some areas that I
> would like to work on are:

> 1) I’d like to increase the conceptual nature of my class without
> losing the quantitative component. 

That sounds like the right way to look at it.  You need both.

> What is an appropriate balance to
> the number of conceptual type questions versus the number of
> quantitative problems found on a test (or even a homework assignment)
> for a high school physics class?

That is *not* the right way to look at it.  It's not an either/or 
proposition.  The relationship between the quantitative angle
and the conceptual angle does *not* involve classifying any
given problem as conceptual versus quantitative.  That might 
sorta sometimes work for a problem that can be solved in a single
step ... but any real-world problem involves multiple steps, some 
of which are quantitative, some of which are conceptual, and some 
of which are both.

>  Obviously, “plug
> and chug” is easier to teach than the conceptual nature of physics.
> Show the students the pattern to a formula and they can find numbers
> to plug into an equation with very little effort.   

That may be obvious in connection with end-of-chapter problems
that have been cooked to the point where they yield to one-step
plug-and-chug solutions.  However, it is far from obvious -- and 
indeed far from true -- in connection with real-world problems.  
Anybody who thinks that real-world problems can be solved by 
plug-and-chug "with very little effort" (or solved that way at
all) has spent way too much time inside the ivory tower.

There's a lot more I could say about this, but I forbear.

> 2) Remaining objective in grading questions that are qualitative. I
> don’t always have time to make out rubrics for every question. What
> characteristics do you look for in short essay answers? 

I design the question so that it's obvious whether the student
understood the point or not.  Example: moment of inertia of a
cube:
  http://www.av8n.com/physics/wig-eck.htm

Example: block on fall
  https://carnot.physics.buffalo.edu/archives/2011/1_2011/msg00596.html

For completely open-ended problems, you can have the students
work in groups and evaluate each other's solutions.  Peer
pressure can be a tremendous motivator, often better than grade
pressure.

> 3) Preparing students for these types of test questions. What
> techniques do you use to help them develop the skills necessary to
> think conceptually?

The usual "building block" approach:  Start by working on
one skill at a time, then putting them together.  For more 
on this, see
  http://www.av8n.com/physics/thinking.htm

Also beware that students are (in many cases) so accustomed to 
not thinking in class that if you tell them they are expected
to think, they simply will not believe you the first time, or
the second time.

> 4) Finding resources that show the conceptual nature of physics.
> Typically, when I look for conceptual type questions, I either use
> Hewitt’s book 

I know Hewitt's book is called "Conceptual" ... but that does not 
make it so.  It rarely calls for more than rote regurgitation.
And sometimes when it manages to make a conceptual point, it
gets it wrong.
  http://www.av8n.com/physics/hewitt.htm

I know there are some people on this list who use "conceptual"
as a euphemism for "too clueless to do a calculation" ... but
don't expect me to accept this usage.  To me "conceptual" means
almost the opposite:  It means doing the calculation *and* 
understanding what the calculation means.

> or use <physicsclassroom.com>.

Can you give an example of a "conceptual" problem from that site?
The last time I looked at that site, all I saw was a load of plug-
and-chug exercises at the most debased level, or perhaps one small
step above that level.

> 4) Finding resources that show the conceptual nature of physics.

You can bring up scaling laws early and often.  Scaling laws are
conceptual *and* semi-quantitative.  They are age-appropriate
and very very practical.
  http://www.av8n.com/physics/scaling.htm

Also almost any task having to do with symmetry and/or conservation
is an opportunity to put qualitative reasoning to good use.

The famous "bridge" problem
  http://www.av8n.com/physics/img48/bridge.png
yields to qualitative reasoning (plus the principle of virtual
work).

The famous "yo-yo" problem 
  http://www.av8n.com/physics/ill-posed.htm#sec-yo-yo
can be solved in multiple ways, including more than one type
of qualitative reasoning.

Most importantly:  Almost any real-world problem involves a
mixture of conceptual and quantitative reasoning.  There are
innumerable examples.  Some familiar examples include
 -- The physics of cars.
 -- The physics of bicycles.
 -- The physics of boats.
 -- The physics of aircraft.
 -- The physics of weather systems, fronts, et cetera.
 -- The physics of the "energy industry".
 -- etc. etc. etc.

You could pick one of these as a _theme_ and spend an entire
year working it over, looking at it from many different angles,
with gradually increasing detail and precision.