Newton's Laws of Motion: Newton's Third Law

Lesson 4: Newton's Third Law


Newton's third law

Newton's third law says that for every action, there is an equal and opposite reaction.

This means that whenever an object moves, pushes or presses another object, the second object reacts by returning the same amount of force.

Objects react by creating resistance, or pushing back. Here are some examples in which this law applies…

A rocket launch

In order for rockets to reach space, they have to be propelled with great force. For this reason, their engines emit gasses downward, toward the ground.

If the rocket is Object 1 performing an action, then the ground is Object 2. The ground reacts with the same force, pushing the rocket upward. This is how it gets launched into space. 

Jumping and swimming

When a person jumps into the air, the force from their body is pushing downward, toward the ground. The ground pushes the person upward, into the air–sort of like the rocket! If the person uses less force, they won’t jump as high. 

If you’re swimming in a pool and you push the water with your arms and legs, the water reacts by propelling you forward. The more force you use, the further and faster you’ll swim. 

A fun exercise

Hopefully this tutorial has helped you to understand Newton’s three laws of motion. Take the final quiz to see how much you learned!