Topic 3 Third Law

Newton’s 3rd Law states that for every action, there is an equal and opposite reaction.Whenever an object exerts a force on another object (the action), the second object exerts an equal force in the opposite direction on the first object (reaction).

newton's third law - action and reaction

Swimming

How is swimming an example of Newton's Third Law? What are the actions and reactions when they swim? Click on the picture above to find out more!

How is a rocket launch an example of Newton's Third Law? What are the actions and reactions involved in a rocket launch? Click on the picture above to learn more!

Rocket Launch

• Click the link above to watch a swimmer in action and identify the action and reaction forces involved in their swimming motion.

When a swimmer moves through the water, they are constantly demonstrating Newton's Third Law of Motion. As the swimmer pushes the water backward with their arms and legs (the action), the water pushes the swimmer forward (the reaction).This interaction occurs because when the swimmer exerts a force on the water, the water exerts an equal and opposite force back on the swimmer. The greater the force the swimmer applies to the water, the faster and farther they propel themselves forward. This principle is not only essential for swimming but also illustrates how forces interact in fluid dynamics, enabling swimmers to efficiently navigate through the water.When a swimmer pushes off the wall of the pool, they are also demonstrating Newton's Third Law of Motion. As the swimmer exerts a force against the wall with their feet (the action), the wall exerts an equal and opposite force back on the swimmer (the reaction).

Swimming

When a rocket's engines ignite, they burn fuel and expel exhaust gases downward at high speed. This action of pushing the gases down is the action force.According to Newton's Third Law, the rocket experiences an equal and opposite reaction. As the exhaust gases are pushed downward, the rocket is propelled upward. This upward force allows the rocket to lift off the ground and ascend into the atmosphere. The rocket continues to push exhaust gases downward as long as its engines are firing, producing a continuous upward force. This consistent action-reaction pair is what enables the rocket to overcome Earth's gravity and reach space.

Rocket Launch

Click on the link above to watch the launch of a SpaceX Falcon Heavy rocket carrrying NASA's Europa Clipper spacecraft. (Oct. 14, 2024).