Find two supports such as two trees or two chairs on opposite sides of a room that are 3-6 meters (10-20 ft) apart. Tie a piece of string to one of the supports. Next, inflate the balloon. Pinch it shut while your friend tapes a 3 cm (1 in) piece of drinking straw to the side of the balloon as shown. While still holding the balloon shut, have your friend to run the string through the straw and tie it to the other support.
Release the balloon and watch what happens.
What Happened: When you let the balloon go, the contracting rubber forced air out of the neck. This was the action. At the same time, the balloon was pushed forward. This was the reaction. Newton’s third law is at work again.
This is the principle that allows a rocket to work. When fuel in a rocket is burned, gases are produced by the burning fuel. These gases rush out of the nozzle of the engine. The downward push of these gases is countered by an opposite upward push on the rocket which causes the rocket to lift off the launch pad.
