The Blowgun as a Teaching Tool

One of the first things I acquired through the bureaucratic school district purchase requisition process was Pasco Scientific's Lenz's Law Demonstrator. As a newly-minted classroom teacher, I found the prices in supplier catalogs to by eye-popping. (I have a better understanding of the economics and value propositions of those prices now.)

I used the satin-finished aluminum tube and magnets for its intended purpose right away. 

I then added some intrigue/obfuscation by hiding a stack of potent neodymium magnets inside a hollowed out red whiteboard marker. I told students that the tube could detect the marker's color and try to stop the fall of the red marker. To "prove" my point, I would drop an unmodified green marker through the tube showing that the tube offered no resistance. Some students would demand up-close inspection. They found the red marker was heavier: the heavier marker fell more slowly!

I typically ran this demo on the first day of school as part of my "Physics Begins with an M" first day of school lesson. The explanation had to wait until second semester, when we studied magnetism.

Since this demo was so costly, I felt I had to add value. I found I could balance it vertically on my classroom floor to demonstrate unstable equilibrium. And when it toppled over, the sound it made could pierce your soul. Students would emit involuntary screams. 

Holding the tube with thumb and forefinger at various places while gently bouncing it on the tile floor produced different notes as different resonance modes were activated. 

But one fine day in the spring of 1995, I noticed that our current crop of Whytebord markers just barely fit into the tube. In a moment of serendipity, loaded one into the tube and blew it out toward a door in my classroom. Hard. Upon impact, the marker exploded into a shower of plastic shards and parts. My students and I all needed a moment to compose ourselves.

"Do it again!" cried a voice in the crowd. I began saving ever marker that ran out of ink. I should have asked colleagues for theirs, too. And I set about scheming ways to integrate blowgun physics into my curriculum.

Mounting the tube on table clamps and setting photogates at the end revealed that speeds in excess of 55 mph were easily repeatable. Setting up a cardboard box (or lid) to stop the marker added flare when the marker sailed through said box. Knowing the exit speed and tube length allowed for a calculation of acceleration.

When summarizing Newton's laws, we talked about their relevance at the beginning (marker at rest), time in the tube (acceleration), flying through the air, and coming to a stop. Delightful!

We tried longer PVC tubes during the energy unit. The weren't always as true or smooth. But at double the length, speeds of over 100 mph were possible.

Inevitably students wanted to try. With sanitizing measures, we made it happen. But their blowgun skills were weak! They never matched my own speeds. When it comes to blowing hot air around, I'm a champ.

Using a transparent plastic tube allowed for the search for the temporal midpoint by setting photogates along the length of the tube. It seemed the possibilities were limited only by one's imagination.

After demonstrating my blowgun physics applications to the Northern California and Nevada Section of The American Association of Physics Teachers at their Fall Meeting in 1995, I wrote an article for The Physics Teacher.

"The Blowgun as a Teaching Tool" was published in February, 1996. The first page looked like this:

UPDATES [2021]: Here are some remote teaching / distance learning lessons posted on The Blog of Phyz.

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