What is Newton’s Third Law of Motion?

Newton’s Third Law of Motion is one of the fundamental principles of classical mechanics. It states: “For every action, there is an equal and opposite reaction.” This means that whenever an object exerts a force on another object, the second object exerts a force of equal magnitude but in the opposite direction on the first object. These forces always act on different bodies and never cancel each other.

For example, when you push a wall, the wall pushes back with the same force in the opposite direction. Similarly, when a rocket launches, the engines push gas downwards, and in response, the rocket is pushed upwards with an equal force. This principle explains the motion of objects in everyday life, engineering, and space exploration.

Newton’s Third Law is essential for understanding interactions between objects, such as walking, swimming, or driving a car. When your foot pushes backward on the ground, the ground pushes your foot forward, enabling movement. In sports, hitting a ball or rowing a boat also follows this principle: the forces are equal and opposite, resulting in motion.

It is important to note that this law does not describe the magnitude of motion but rather the relationship between the forces. The objects may have different masses, causing them to accelerate differently according to Newton’s Second Law (F = ma), but the forces remain equal and opposite.

In summary, Newton’s Third Law of Motion—for every action, there is an equal and opposite reaction—explains the mutual forces between interacting objects. Understanding this law is fundamental in physics and everyday science, helping students connect theoretical concepts with real-world examples like rockets, vehicles, and human motion.