Conceptual Physics

Paul G. Hewitt


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Getting to Rainbows

In a recent tour of several high-school classrooms where conceptual physics was being taught, I was surprised to find instruction still on kinematics in mid October. This was not in classes for future scientists and engineers, but in conceptual classes where most students encounter their first and last physics course. I find this much time on kinematics disappointing, for although displacement, velocity, and acceleration are basic concepts in mechanics, I've found post-kinematics concepts more important and appreciably more fascinating to students.

Presumably, an important goal in the conceptual course is an overview of not only mechanics concepts, but also those of matter, heat, vibrations and waves, electricity and magnetism, light, perhaps quantum phenomena, and maybe culminating with radioactivity and nuclear power. With so much time devoted to kinematics, is there any time later for "rainbows?" Isn't the enthusiasm of a course best established at the beginning-when students do or don't get hooked on physics? Is kinematics the best hook? There are good reasons for beginning with kinematics, but can't velocity and acceleration and their distinctions be briefly treated, with a quick move to Newton's laws, momentum, energy, and satellite motion, where these concepts are more interestingly developed?

Why so much time on kinematics? I found the answer; the teachers' love affair with the wonderful tools of graphical analysis. Like the astronomer whose love is more for telescopes than stars, teachers are more enamored with ticker timers, sonic rangers, and computers, than the concepts they illustrate. Hence kinematics gets overtime. Teachers love graphical analysis. But I think students, given a choice between learning to plot motion graphs and learning to analyze rainbows, would prefer rainbows.

Graphical analysis needn't be cut, just reassigned. Consider the spiral teaching strategy championed by Al Baez two decades ago-touch on a concept lightly, and return to it later. Can't we resist the temptation of extended initial time on kinematics and instead begin with a light treatment and progress though and beyond mechanics? Then at the end of the course, after "rainbows," couldn't we bring out the tickers and computer graphing tools, set the plow setting a bit deeper, and return to the kinematics that was lightly treated in the course's beginning?

Let's not get bogged down with kinematics. Most of the fascination of physics lies beyond.

Good Energy!

        Paul G. Hewitt