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

The Core Principle

This law explains how forces always come in pairs. When you push an object, the object pushes back on you with the exact same amount of force. Even though the forces are equal in size, they act in opposite directions. These forces are called action and reaction forces.

Real-World Examples

You can see this law in action every day:

• Walking: When you walk, your feet push the ground backward. The ground pushes your feet forward with an equal force, allowing you to move.
• Swimming: A swimmer pushes the water backward with their hands. In response, the water pushes the swimmer forward.
• Rocket Launch: A rocket engine pushes hot gas downward at high speed. The gas pushes the rocket upward with an equal force, causing it to lift off.

Key Characteristics

It is important to remember that these forces act on different objects. If Object A pushes Object B, Object B pushes back on Object A. Because the forces act on different bodies, they do not cancel each other out. This is why motion is possible.

Mathematical Understanding

In physics, we write this law as: FA on B = -FB on A. The negative sign represents the opposite direction of the force. Both forces exist at the exact same moment. If the action stops, the reaction stops instantly.