What is Newton's Third Law of Motion?

Newton's Third Law of Motion states that for every action, there is an equal and opposite reaction.

This means that whenever one object exerts a force on a second object, the second object exerts a force of equal magnitude but in the opposite direction on the first object. Imagine you are standing on a skateboard and you push against a wall. The force you apply to the wall is matched by an equal force from the wall pushing back on you, causing you to roll backwards.

This principle can be observed in many everyday situations. For example, when you jump off a diving board, you push down on the board with your legs. The board pushes back up with an equal force, propelling you into the air. Similarly, when a bird flaps its wings, it pushes air downwards. The air pushes back up with an equal force, allowing the bird to lift off the ground.

Newton's Third Law is crucial in understanding how forces work in pairs. These pairs of forces are often called "action-reaction force pairs." It's important to note that these forces act on different objects and therefore do not cancel each other out. Instead, they result in changes in motion for the objects involved.

In physics problems, identifying these action-reaction pairs can help you analyse the situation more effectively. For instance, if a car is driving forward, the tyres push backwards against the road. According to Newton's Third Law, the road pushes forward on the tyres with an equal and opposite force, propelling the car forward.

Understanding this law helps explain not only simple actions like walking or swimming but also more complex phenomena such as rocket propulsion. In a rocket, the engines expel gas downwards, and the equal and opposite reaction force pushes the rocket upwards, allowing it to launch into space.