June 2007 (Volume 16, Number 6)

# Letters

## Can Simulations Really Teach Physics?

I want to comment on the letter “Simulations Teach Real Physics” in the April 2007 APS News by Henderson Cole, and the Viewpoint by Alan Chodos in the February 2007 APS News. The former states that “events in a real laboratory happen too fast to observe the physics,” so it is better to learn by using a physics simulation software package, and watch it in slow motion. He specifically mentioned measuring the gravitational acceleration constant g.

About 55 years ago, my high school physics teacher devised an experiment to measure g using a ball bearing slowly rolling down an improvised inclined plane (a 16-foot section of half-round rain gutter dusted with flour to show the oscillating trajectory). Measurements gave a value of g that was about 30% too low. More precise measurements confirmed this low value. My teacher and I decided that perhaps the “inertia” of the rolling ball bearing slowed it down. I found a college calculus book in the school library, and after about a week of intense study, learned enough math to understand and calculate the rotational inertia of the ball bearing, and get the accepted value of g. The enjoyment was in the quest for the answer, not learning it in a simulation. How can one appreciate a lab on electricity without recalling the acrid smell of an overheated Allen-Bradley resistor, or the sweet aroma of ozone from sparks.

Doing physics lab experiments using canned software simulations is about as exciting as picking up a crossword puzzle, only to find that the answers have already been penciled in. The virtue of using virtual experiments as a teaching tool in high schools should be limited to comparing the measured results to the expected results, not as a substitute for real physics. Teaching the fundamental laws of physics in high schools requires observation and measurement before simulation. Watching a current-carrying wire move in a magnetic field is more instructive than just plugging the current and field values into a simulation of the Lorentz Force Law. Can a force really be perpendicular to both the current and the magnetic field? Seeing it is better than reading about it. Doing it is even better. I recently gave small battery-powered DC electric motor kits to every student in the AP physics class at my former high school. I can understand why students who learn (memorize?) physics using virtual physics experiments might perform better on AP physics tests. And I can understand the inherent danger in exposing some students to electricity in the lab (These are often the same ones who never learn AAA (Always Add Acid) in the chemistry lab). But the original basis for physics was to explain real world phenomena using tools such as mathematics and reasoning. Viewing virtual experiments on a computer is no substitute for doing the real thing, even if the equipment has to be improvised.

Robert Shafer
Los Alamos, NM

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