Purpose: To demonstrate that vertical acceleration is independent of horizontal motion.

A spring actuated gun aimed with a laser sight at a model of a monkey suspended by an electromagnet on a high pole. When the gun fires a 2.5 cm ball bearing, it passes a photogate causing a magnetic field to briefly cancel the magnet holding the monkey, thus releasing the "monkey." Since the acceleration downward of the monkey and the ball are the same, the ball's parabolic trajectory and the monkey's vertical trajectory meet near the floor.

Explain that when the monkey sees that the gun is aimed at him, he decides to fool the hunter by letting go at the instant he sees the flash of the gun. This, of course, is a grave error due to his ignorance of the independence of vertical and horizontal motion.

References: