The Monkey and the Hunter Demo

Theory

Gravitational forces from the earth affect all masses in the same manner. In other words, the acceleration due to gravity (g=9.81 m/s*s) is constant regardless of the mass of the object. Thus, if two objects are placed a given horizontal distance apart, that distance will remain constant as they accelerate towards the earth over a short distance. This is because they both accelerate at the same rate and their displacement towards the earth is identical at all points in time.

If one were to assume that the projectile gun and the target would begin falling at the same time, their position relative to each other would remain constant according to this theory. Furthermore, if one of the objects had an initial velocity toward the other, it would move toward its target at that constant velocity for the duration of the fall. If that were so, a projectile launched from a gun at the same time as the target is dropped, would automatically strike the target. This assumes that gravity begins accelerating the projectile at the exact same time as it begins accelerating the target.

Apparatus

The equipment needed for this demo is a Pasco "Shoot the Target" set-up with photogates.

Procedure

The first thing to do is set up the monkey. This must be done by placing the magnet and the target on the stand and securing them. The height can be adjusted to any height necessary.

The shooter is set up a given distance away from the target and aimed at it. Then, when the system is turned on, without moving anything, the projectile is fired at the target. Simultaneously, the target is dropped from its position. The projectile will leave a mark on the target where it hit.

This procedure is repeated for different distances and different heights with the deviation from the center of the target always marked.