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Re: [Phys-L] The Make-Believe World of Real-World Physics

You might be a redneck physicist if ... you think it makes sense
to ask a multiple-guess question about «the force» involved when
a large truck smashes into a small car.

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

I wrote in part:

IMHO, telling students the subject is scary and counterintuitive
is /not/ constructive.

On 07/17/2013 03:32 PM, Chuck Britton wrote:

Does anyone here really think that getting beginning students to
fully grasp the First Law is trivial?

That's a slightly different question than the one I was trying to
address. Tangential remark: I'm going to ignore the word "fully",
because personally I don't understand anything "fully", and AFAICT
neither does anybody else ... student or otherwise.

At this point, we are left with at least three things to ask about:
a) The beginning of the road.
b) The potholes along the road.
c) The end of the road.

A) We agree that at the beginning, students find physics to
be highly counterintuitive, or they would, if they even knew
what questions to ask.

B) We agree there are lots of nontrivial potholes along the road.

C) The question that most interests me is whether the ideas
/remain/ counterintuitive. I believe in the proverb that
says:
Education is the process of cultivating your intuition.
I see it as my job to /make/ this stuff become intuitive,
i.e. to get students to the point where the right answer
seems intuitive, indeed inescapable.

This is a hard job, and all-too-often I fail at parts of
it, but I keep trying.

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

Whenever students predictably make a certain mistake, it's
a sign that something is counterintuitive. To me, this
is a red flag. It identifies something that we -- the
instructors -- need to work on.

I consider the FCI to be one-sided, in the sense that a low
FCI score is a highly meaningful wake-up call ... even if
the meaning of a high FCI score is much more debatable.

We can probably agree that any debate over the meaning of
high FCI scores is premature. That would be a nice problem
to have. The more immediate problem is that in the PER
literature, people brag about tiny FCI gains. Their
post-test scores are "better" in relative terms, but
still terrible in absolute terms.

To my way of thinking, this is not OK! This is a problem
that needs fixing. It is not OK to say that the subject
is difficult and counterintuitive and leave it at that.
It is my job to /make/ it become intuitive. This seems
like an achievable goal. Any self-respecting physicist
should be able to answer simple conceptual questions on
sight, in less time than it takes to ask the question,
with very high reliability. This applies to FCI questions
in particular, and also to questions a lot harder than
that.

I'm willing to accept that some parts of the topic are
non-intuitive, especially when it comes to terminology.
Even when the /concept/ is intuitive, the /terminology/
we use to describe the concept is usually artificial and
arbitrary. Arbitrary things are, almost by definition,
not intuitive.
*) Ideally the terms will be logical and mutually consistent,
so that even if they are unfamiliar, they will be at worst
neutrally non-intuitive ... as opposed to actively confusing,
inconsistent, and diametrically counterintuitive.
*) Sometimes there is a bigger problem, such as a conflict
between technical terms and the corresponding vernacular
terms. I accept that students will always have trouble,
especially at first, with the conflict between physics
energy and vernacular "energy", physics conservation and
vernacular "conservation", et cetera. This problem is
not preventable, but it is survivable. Any student with
half a brain has already figured out that any given word
has multiple meanings, depending on context.
*) On the other hand, some of the current terminology is
terrible for no good reason. To my way of thinking,
this is a major opportunity for improvement. We can
make physics more intuitive by cleaning up some of the
terminology, such as:
-- two different definitions of "acceleration"
-- two wildly inconsistent definitions of "gravity"
-- two very different definitions of "adiabatic"
-- four or five wildly inconsistent definitions of "heat"
-- et cetera. There is really no excuse for inconsistent
terminology *within* a narrow field.

The question remains: Is physics, hard, counterintuitive,
and/or scary? Again I say it depends on whether you are looking
at the beginning of the road or the end of the road. Lots of
problems start out hard, but they don't need to stay hard.

For example: It took me years to even /notice/ that there was
something fundamentally wrong with the way intelligent people
use the word "acceleration". Then it took a huge amount of
effort to sort out the problem, eventually resulting in a
clean distinction between scalar acceleration and vector
acceleration. Similarly it took me years to even /notice/
that there was something very wrong with the usual textbook
treatment of "gravity". Then it took a huge amount of effort
to sort out the problem, eventually resulting in a clean
distinction between the local g (completely frame-dependent)
the barogenic δg (completely not frame-dependent). Et cetera.

The interesting thing is that once such things get fixed, they
tend to stay fixed. It is almost trivial to incorporate the
fixes into the curriculum. This removes a big burden from
the students. It makes things much, much more intuitive.
-- Holy wars about "heat" go away ... just talk about energy
and entropy instead.
-- Holy wars about whether the astronauts are weightless
go away ... it's frame-dependent. No dogmatic yes/no
answer is required, or even permitted. The g-value is
completely 100% frame-dependent.

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

I also recognize that if you want to make something counter-
intuitive, you can always do that. For example, there is an
FCI question that involves a large truck smashing into a small
car.

I claim that if a student gets this right, it tells you very
little. If you ask somebody "how do you know", the best-case
answer is "Oh, I recognize this question. It's intended to
be a stylized question about the third law, so I answered
accordingly." An even more-common answer is "Uhh, well, it
just seemed reasonable."

I further claim that if a student gets this wrong, it also
tells you very little. Part of the problem has to do with
distraction and obfuscation. I'm not saying that the question
is unfair or intentionally deceptive ... but still there is
quite a lot of abstraction, distraction, and obfuscation.
The question tries to pass itself off as a "real world"
question, but it really isn't, for the following reasons:
-- I've never seen anybody do an experiment of this kind,
with a force-transducer between the car and the truck.
-- If you tried it, you would discover that there's no such
thing as "the" force in such a situation; there are a whole
lot of wildly varying forces. So the question is asking
about something that does not actually exist. No wonder
students think physicists are crazy.
-- Even if such a force existed, it would not be the whole
story. One might reasonably wonder why we are asking about
one *part* of the force exerted on the truck, namely the
part exerted by the car, when common sense says we should
be more concerned about the *total* force on the truck.
-- Most of the real-seeming details in the question do not
matter. The fact that the truck is a truck doesn't matter.
The fact that the car is a car doesn't matter. Et cetera.
-- One key fact about the real-world situation is *not*
consistent with the stylized question that is being asked:
In the real world, as a result of the collision, both
vehicles wind up at rest. This is *not* the result you
would calculate based on the third law. This is not to
say that the third law is wrong, but rather that we are
asking a Make-Believe question. Even though we have painted
a real-world picture, we are asking an abstract, artificial,
Make-Believe question about the picture.

Again, I'm not saying that the question is unfair. In the
real world, questions virtually never arrive at my desk in a
form that can be solved by direct application of this-or-that
fundamental law of physics. There is always some degree of
disguise, abstraction, distraction, and obfuscation. Students
need to learn how to handle this.

FCI questions are thinly-disguised questions about the laws
of motion. Students need to learn how to strip the disguises.

Constructive suggestion: Teach students to look at each and
every question in more than one way. This has tremendous
advantages, because very often, a disguise that is deceptive
from one angle becomes utterly non-deceptive from another
angle.

Also: Speaking of abstractions: Physics is all about
abstractions. Consider the wave in this diagram:
http://www.av8n.com/physics/reality-reductionism.htm#fig-reality-wave-mixed-media
-- The wave is an abstraction. The wave has properties of
its own, separate from the properties of the medium. The
wave on the rope is recognizably the same as the wave on
the chain. The wave is the same, even though the medium
has changed.
-- Energy is an abstraction. The energy in the wave moves
from left to right, even though the medium does not.

Similarly: Electrical charge is an abstraction.
http://www.av8n.com/physics/reality-reductionism.htm#sec-charge

Simplicio says: Physics is hard and counter-intuitive because
of all the abstractions. Teachers should find ways to dumb
down the course, tip-toeing around the abstractions, so the
students can think exclusively in terms of concrete, tangible
things.

Salvatio says: Embrace the abstractions. Physics is all about
abstractions. The abstractions give physics power and elegance
and unity and grandeur. The first few weeks of the introductory
physics course typically focuses on the mechanical motion of
material particles, which is maybe OK as a starting point, but
not as an ending point. Sooner or later -- preferably sooner --
it is necessary to move on to a higher level of thought. The
more you focus on concrete non-abstract things, the more you
are going to miss the important fundamental physics.

You have to trust the students, to trust that they can handle
abstraction and symbolism. They already have this skill in
general; you just have to teach them how to apply it to
physics. If you tell me the students are so brain-damaged
that they cannot play with dolls, stuffed animals, or toy
trucks, then I will believe they cannot handle abstraction
and symbolism; otherwise I don't believe it.

Abstraction is not the same as unreality. The wave on the
rope is a real thing. It is an abstraction, but it is as
real as anything can be.
http://www.av8n.com/physics/reality-reductionism.htm