The activity described below works well for all students. The student with a visual impairment can best experience the activity as the person who has a chance to release the balloon*. Also beneficial is an opportunity to be at the end when the balloon rocket arrives. The whole class will want to do this activity again and again.
*NOTE: Balloons should NOT be used by students with latex allergies. If in a latex-free school, use mylar balloons.
￼Action force - force acting in one direction
Reaction force - force acting in the opposite direction
Action and Reaction
Forces always act in pairs. The two forces act in opposite directions. When you push on an object, the object pushes back with an equal force. Imagine a person sitting in a rolling chair at a desk. When the person sitting in a rolling chair pushes on the desk, this push or force is the action force.
Now, the desk pushes back against the person with a force of the same size. This reaction force will cause the rolling chair to move backwards. Notice that the two forces act on different objects. The action force acts on the desk. The reaction force acts on the person.
Newton’s Third Law
Newton’s third law of motion describes action and reaction forces. The law states that for every action force, there is an equal and opposite reaction force. Imagine hitting a tennis ball. The racket exerts a force on the ball. This is the action force. The ball exerts an equal and opposite force on the racket. This is the reaction force.
Newton’s third law explains how many sports injuries are caused. The more force you use to a hit a tennis ball, the more reaction force your arm receives from the racket. Every time your feet hit the ground when you are running, the ground hits your feet with an equal and opposite force.
Balloons and Rockets
Newton’s third law explains how balloons and rocket engines work. When the neck of an inflated balloon is released, the stretched rubber material pushes against the air in the balloon. The air rushes out of the neck of the balloon. The action of the air rushing from the balloon pushes against the balloon, moving it in the opposite direction.
When rocket fuel is burned, hot gases are produced. These gases expand rapidly and are forced out of the back of the rocket. This is the action force. The gases exert an equal and opposite force on the rocket itself. This is the reaction force. This force pushes the rock upward.