The Physics

A spud gun is simply awash in science. We started out with a discussion of pressure, energy, and work. Conservation of energy states: “Energy is neither created nor destroyed but rather changes forms.” Nuclear power is an exception to that axiom, but we didn’t want to get too deep into the weeds.

We blew up a balloon and let the air out very slowly. The noise sounded like a fart, so you can imagine what a crowd-pleaser that was. Then we filled a balloon and released it to jet about the classroom. Finally we blew up a balloon and burst it with a pin. In each case the balloon held roughly the same amount of energy, it was just released in different ways.

We then discussed the three elements necessary for combustion—fuel, oxygen, and heat. Air the gun out well, stuff a spud down the bore, then seal it up and charge it with propane and you have two of the three elements, hit the grill igniter to add the magic spark and…