Wednesday, September 13, 2006

I'm done with kinematics

When I started teaching high school physics (during the Reagan Administration), I felt an obligation to "reinvent the wheel." I didn't blindly follow the sequence of chapters laid out by whatever textbook the school had. I was in charge of the curriculum! I wrote my own handouts, homework, tests, etc.

But what I turned out was a pretty true reflection of the introductory college courses I had most recently finished. Mostly the same topics. Mostly the same sequence. It wasn't so different from the textbook's sequence.

I had a whole unit on vectors. It followed my robust unit on "preliminaries" (scientific notation and so on). After vectors was the Month of Kinematics. One-dimensional, two-dimensional; graphical and algebraic. Ticker-tapes, falling bodies, the monkey gun... what's not to love.

The trees were losing their leaves before any mention of Newton was made in my class.

But I noticed a few things. My students never thrilled to the lessons of kinematics as I did. It's difficult, abstract material if you go into deeply. It took the human intellect about 2000 years to figure this stuff out. And we start the year in physics with it. And the year usually ran out before we got to how rainbows work or why the sky is blue.

I was thinking about slimming down my kinematics coverage when I saw Paul Hewitt refer to kinematics as a "black hole" in a Physics Teacher editorial.

Now I speed through motion. I cover it as much as I think it needs to be covered, then move on. (Sorry about the puns, but I'm a physics teacher; we breathe puns the way most people breathe air.) Newton's name will be uttered into air that could be 100F here in Sacramento. The leaves are still green in New England.

There are other ways to handle the problem of not getting to rainbows. The original PSSC program started the year with optics, an approach that galvanized a following even after PSSC abandoned it.

My point is to go easy on kinematics in particular and mechanics in general. First-year high school physics students don't need it to that depth.

The first year I went with the slimmed down kinematics, I held my breath and wondered which part of the sky would fall down. When June rolled around, I noticed that the whole sky was still up. And my students knew why it was blue.


Anonymous said...

I totally agree with the unintended consequences of kinematics (which we see as easy, because it doesn't really require physical reasoning, just algebra; unfortunately, they think it's hard for exactly the same reason!). I don't teach it to conceptual physics students until the spring (after osc. and waves, sound, optics, and circuits), and this is the mechanics sequence that I'm using for my senior-level students:
- preliminary stuff (3 days max)
- 1D kinematics, no acceleration
- 1D and 2D statics
- kinematics with acceleration
- dynamics
- momentum conservation
- energy conservation

My hope is that the "big picture" is grouped into "situations with a=0" and "situations with nonzero a." This is my attempt to group the concepts physically and not mathematically - we'll see how it works!

Anonymous said...

I agree.

I teach
- velocity
- momentum and its conservation
- impulse-momentum
- falling objects
- conservation of energy
- rotation
- sound
- lens optics
- color theory
- electricity and magnetism

I have started with optics and sound, but I am trying starting with mechanics again. The math teachers and I are trying to work together so that the students will get similar presentations in two classes and double the practice. Maybe that will help.

Marc "Zeke" Kossover

MV said...

You need not work out too many application and understanding type questions in Mechanics if time is limited. However,you may insist that the students should work out some typical and comparatively interesting problems related to the topics taught.

Anonymous said...


For years, some of us in the UMass Physics Education Research Group ( have been arguing that the Physics Department should change its introductory physics majors' curriculum around. Optics and thermodynamics are both mathematically simpler and, hopefully, a little more interesting to students. Thus, they should go in the first semester.

Unfortunately, the Physics Department has never been quite brave enough to try it. The suggestion sounds a little too... heretical... for them.


Dean Baird said...

I don't pretend to know what the politics are that surround the sequencing of intro physics at a major university.

It seems there would be more leeway at that level given that the students have seen physics in high school prior to matriculation. Alas, inertia cannot be ignored since the professors are there to conduct research; instructional excellence may not be a priority. Tinkering with the sequence may cut into their research time.