Newton’s Third Law of Motion

Basic Understanding of Newton’s Third Law

Newton’s Third Law of Motion states: For every action, there is an equal and opposite reaction.
This law means that any force exerted on a body will create a force of equal magnitude but in the opposite direction on the object that exerted the first force.
It’s important to note the forces act on different objects. If object A exerts a force on object B, the reactive force of object B acts on object A.

Walking or running involves pushing the ground backwards (action) which in turn pushes us forwards (reaction).
When a swimmer pushes the water backwards, the water pushes the swimmer forward.
Rocket propulsion operates on this principle. Rockets push gases downwards; in response, the gases push the rocket upwards.

Newton’s Third Law helps explain why changes in motion occur. It articulates the relationship between forces, showing that they always come in pairs.
The law also explains the principle of conservation of momentum - the total momentum of a system remains constant if no external forces are acting on it.
The concept of balanced forces is inherent in Newton’s Third Law. If two equal forces are acting in opposite directions on a body, their effects cancel out and the body remains in its original state of motion.

It’s important not to confuse the pairs of forces in action-reaction pairs with the forces on an individual object resulting from interactions with different objects.
The reaction force is not a response to the action force in the sense that it only occurs after the action. Rather, both forces occur simultaneously.
Just because the forces are equal does not mean their effects are. The effect of the force (acceleration, deformation etc.) is influenced by factors like the mass and material properties of the objects. For instance, a car hitting a wall applies the same force to the wall as the wall applies to it, but the car is more affected due to its properties.