PURPOSE: To demonstrate the third law of motion.

DESCRIPTION: Air is compressed in the rocket by means of the pump; when the air is released, the rocket rises by a small amount. If a small amount of water is poured into the air compartment from the squeeze bottle pictured at the right and air compressed in the rocket to the same pressure as before, the rocket will rise very high when released. Due to its greater mass, the water exhaust has more momentum than the air; thus more reaction force is applied to the rocket by the exhausting water.

SUGGESTIONS: ONLY used in large Lecture Halls. BE CAREFUL where you aim the rocket! DO NOT HIT the rear projection screen above the blackboards!!

REFERENCES: (PIRA 1N22.20) See Demonstration Reference File for a number of articles on various aspects of rocketry.

EQUIPMENT: Water rocket with water, as photographed.

SETUP TIME: None.