# Demo Content

Monkey Gun

Purpose:
To demonstrate the independence of vertical and horizontal motion.

Equipment:
Monkey gun (barrel with electromagnet) "bullets" or "darts" (cylindrical Al plugs) "Monkey" (bull's eye lid) DC power supply laser for sighting 2 table clamps

Equipment Location:
Mara_Left

Procedure:
Mount Monkey Gun to table (Mara) or chalk tray (M208) using 2 clamps. Using two clamps greatly improves the stability of the aim of the gun when it is fired. Load the gun with bullet. Hang Monkey from ceiling using electromagnet. Attach laser sight to barrel of gun and aim a couple cm above bull's eye. Forcefully blow on tapered end of gun barrel. Adjust aim as necessary.
You can use 2 volunteers with the following story. Imagine blow-dart hunters trying to kill a monkey. Since the dart will fall as it travels, one would have to aim above the monkey to hit it. Figuring out how high above the monkey to aim is difficult, so our hunters employ a different strategy. The idea is to scare the monkey off the branch right when the dart is shot so that the dart and the monkey fall the same distance. One volunteer is the shooter, and one is the yeller or clapper. The shooter aims straight at the monkey and shoots just as the clapper claps.

Relevant derivations/explanations:
bullet trajectory: yb = vy t - 0.5 g t2 monkey trajectory: ym = H - 0.5 g t2, where H is the original height of the monkey. Imagine there were no gravity. Then since the gun is aimed at the target, from geometry H = vy t. The bullet and the monkey fall at the same rate, so the bullet is always on a collision course with monkey. Note that the bullet is "falling" on the way up. That is, it's accelerating in the downward direction.