Newton came upon his final law, commonly known as the law of reciprocal actions. Simply every action has an equal but opposite reaction. For example, you can’t touch without being touched. A force, a push or a pull, is exerted on each object. One force is applied in a forward direction, while the other is applied in an opposite, or backwards, direction. Forces are like shoes, they always come in pairs.

These pairs are called ‘action-reaction forces pairs.’ They are called Reaction Force A and Reaction Force B. They are drawn in a free-body diagram, as explained in Newton’s Second Law, it’s a diagram showing all the forces acting on an object.

Above: The bird pushes down on the air and the air pushes up on the bird.

In the picture below, the balloon pushes the air down and the air pushes the balloon up .

Right: The Swimmer pushes back on the water, the water pushes foward on the swimmer.