Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: Adding 20th C Physics to Intro classes



Although the idea of doing relativity first is intriguing, I think it is
pedagogically misplaced. Before students can really understand relativity
they need to understand velocity, acceleration, force, position, and time.
In addition they need to gain the various thinking skills that I have
mentioned. This means that they have to be able to use the four
representatons of these concepts: drawings, graphs, descriptions, and
equations. Note equations is the last, because students tend to want to
memorize and use equations, which they will do very inappropriately.
Students have to be able to translate between the 4 representations, and to
use them in solving problems.

Einstein's own explanations of relativity use very concrete examples, but
examples that require understanding of the classical mechanics involved.
When students can not figure out how far away something is by noting the
flash of lightning, and the time delay to the thunder, and the speed of
sound, they are not ready for relativity. Students will often divide when
they should multiply (or the other way around) because they do not
understand velocity.

These problems are not confined to the lower level students, but also happen
with more advanced students. One can explore relativity early on, but the
understanding will necessarily be very superficial, and such exploration may
rely too heavily on memorizing equations. Now if you want to properly
explore mechanics, and then do relativity in place of some other topics,
that would be a reasonable sequence.

Similar problems occurr with respect to other aspects of modern physics.
The photoelectric effect relies on understanding conservation ideas, which
are vital components of formal thinking. Understanding conservation of
energy must precede this topic, and before energy, comes mechanics.
Conservation priciples can be woven into mechanics rather than being a
separate topic, but they do go hand in hand.

I would also point out that the problems of teaching mechanics have been
attacked by many PER groups, so one can achieve good success by following
extablished researched curricula. The relativity first sequence, and other
sequences such as energy conservation first have not been well researched.
This is an example of one of the problems in education. Changes are made
because some teachers think it is a good idea, but without doing the
necessary research to see if the changes work. Since most changes result in
no better results, the disillusioned teachers go back to their old ways, and
just become more cynical. When trying something new, teachers should have
good evaluations in place to be able to see if it works.

I think that a short dose of relativity after mechanics can be a morale
booster for some students, but it is not well understood by most. I
sometimes use it in this fashion as a fun lesson, especially when I have to
be out of town. The Nova series on Einstein is very good, and students can
be safely exposed to it, but I do not expect a major learning experience.

Before replacing traditional topics, I would look to see if there is any
relevant physics education research on the modern physics. I beliver
McDermott has some material that could be used in the effort.
Unfortunately, making improvements requires a team of researchers who are
willing to modify, measure, and adjust curricula. A single teacher usually
does not have the resources to do this alone. Even Mazur had to build his
method on top of the already established FCI evaluation, so he did not do it
just by himself.

John M. Clement
Houston, TX


Please forgive this multiple list posting:

Dear cyber-friends and colleagues;

Last spring I was persuaded to lead a discussion (on October 5) of Physics
teachers/professors on a topic, which can be loosely phrased as “Is it
time to bring HS Physics into the 20th century?” Should we work more to
teach well-established ideas of relativity and particle/nuclear physics
and quantum principles? Most curricula that I see in introductory Physics
(HS, IB or AP) focus on mechanics, waves, E&M, Thermal Physics with some
Atomic/Nuclear Physics.

Part of my acceptance of this was the intriguing CD, Physics 2000, that I
had just ordered and have had some limited opportunity to explore. It
begins with a discussion of relativity.

As I begin to prepare, I thought I would ask if any of you have made use
of Physics 2000, or are adding these non-traditional topics to
introductory Physics (and if so with what success?) or have considered
doing so but shied away or think it is the most foolish idea you have ever
heard or……

Any discussion of the practice or philosophy attached to the addition of
20th c. Physics to an introductory program would be both helpful and
instructive.

Thanks you in advance. Feel free to reply to me in private or make your
thought public here.

Ken Fox
Science Department Coordinator
IB Physics Teacher
Smoky Hill High School
Aurora, CO
kfox@mail.ccsd.k12.co.us