You are likely familiar with the scenario where, upon throwing a ball against a wall, the ball imparts a force upon the wall. Simultaneously, the wall exerts a force on the ball, causing it to rebound. In a comparable manner, Earth exerts a gravitational force, pulling you towards it. What might not be immediately apparent is that, in accordance with Newton’s third law, you are also applying an equivalent force on Earth. This intriguing revelation underscores the reciprocal nature of forces, a fundamental principle elucidated by Newton’s third law of motion. In this article, we will explore Newton's third law, elucidate its principles, and delve into real-world examples and problems to enhance our comprehension.

Newton's third law of motion is encapsulated by the famous phrase: "For every action, there is an equal and opposite reaction." This law emphasizes the dual nature of forces in a system. Specifically, when one object exerts a force on a second object, the second object exerts an equal force in the opposite direction. These forces act on different objects and are known as action and reaction pairs.

Mathematically,

Newton's third law can be expressed as follows:                                                                      

 `F_(action)` = −`F_(reaction)`

​Where

It is crucial to note that these action and reaction forces always occur in pairs and act on different objects.

When a person walks on the ground, the action force is the force exerted by the foot on the ground. Simultaneously, the ground exerts an equal and opposite reaction force on the foot, propelling the person forward.

In swimming, the action force comes from the swimmer pushing the water backward with their hands and feet. The reaction force, in turn, propels the swimmer forward through the water.

When a person jumps, the action force is exerted downward on the Earth. The Earth responds with an equal and opposite reaction force, causing the person to move upward.

In a jet engine, the action force is the expulsion of hot gases backward. The reaction force propels the jet engine and, consequently, the aircraft forward.

Inflating a balloon and releasing it demonstrates Newton's third law. The action force is the air being expelled from the balloon backward, and the reaction force propels the balloon forward.

Now, let's apply Newton's third law to solve problems that involve action and reaction forces.

A soccer player kicks a ball with a force of 20 N. What is the reaction force exerted by the ball on the player?

According to Newton's third law, the reaction force is equal in magnitude but opposite in direction to the action force. Therefore, the reaction force exerted by the ball on the player is also 20 N, but in the opposite direction.

A car collides with a wall, exerting a force of 5000 N on the wall. What is the reaction force exerted by the wall on the car?

The reaction force exerted by the wall on the car, according to Newton's third law, is 5000 N, but in the opposite direction.

A rocket engine expels gases with a force of 1000 N. What is the reaction force exerted by the gases on the rocket?

The reaction force exerted by the gases on the rocket is 1000 N, but in the opposite direction, following Newton's third law.