This demonstration explains the principles of projectile motion and the independence of horizontal and vertical motion. A dart gun is set up on one side of the room, aimed at a monkey hanging from an electromagnet on the other side. The dart gun is equipped with a photogate sensor, which is electrically connected to the electromagnet holding the monkey. When the dart is fired, it passes through the photogate, triggering the electromagnet to release the monkey at the exact moment the dart leaves the gun.
As the dart travels through the air, the monkey falls freely under the influence of gravity. Both the dart and the monkey experience the same gravitational acceleration, meaning they fall at the same rate. Despite the horizontal motion of the dart, the dart and the monkey will meet midair. This occurs because the dart's vertical motion and the monkey's free fall are only influenced by gravity, showing that the dart, when aimed directly at the monkey, will hit the target even as it falls.