Problem 2: Newton's Third Law is also known as the Law of Action and Reaction. The law says "when A pushes B. B pushes on A with the same amount of force but in the opposite direction." A common misconception is that "action" is "cause" and "reaction" is "effect". But it turns out that "action" is a "cause" and "reaction" is another "cause"; each having its own effect. Example: A child jumps and lands on a trampoline. Not action and reaction: As the child lands on the trampoline, the child pushes down on the trampoline and This IS "action", because it is a cause. the trampoline bends downward. This IS NOT "reaction", because it is an effect. This is action and reaction: Action Reaction Cause A child exerts a downward force on the The trampoline exerts an upward force on the trampoline. child. Effect The trampoline bows downward. The child's downward motion stops (or reverses) Now you try. Make sure your action has a thing doing the forcing, a thing being forced, and a direction. (a) A horse-and-wagon are initially at rest. The horse begins to accelerate by walking forward. Action Reaction Cause The horse... The wagon... Effect The wagon... The horse... b) A heavy car collides with a light car. The cars don't stick together. Action Reaction Cause The heavy car... The light car... Effect The light car... The heavy car