Let's imagine a tennis player hitting a ball. It is clear that by making the ball change speed at the moment of impact, the racket is exerting a force on it. But does the ball also exert a force on the racket? The answer is yes. This force has the same intensity as the force the racket exerts on the ball.
According to Isaac Newton, for every action (force) there is an equal and opposite reaction (force). This statement corresponds to Newton's Third Law, known as the Law of Action and Reaction.
Action and reaction situations are very common in our daily lives, they occur whenever we have forces in action and, therefore, in reaction. For example, when we push a car, we exert a force on the car and the car exerts a force on us.
So let's look at some examples of action-reaction force pairs.
Note that Newton's Third Law applies to any situation. In these examples we will only be showing the action and reaction force pairs. No we will show other forces acting on objects.
1 – stone in the sand
– the stone exerts a force on the ground, compressing it, and the latter exerts an equal and opposite force on the stone, preventing it from being accelerated towards the center of the Earth.
2 – person walking – when we walk, we exert a force on the ground which, in turn, exerts a force on our body, pushing it forward and counteracting the force with the weight.
3 – Vase hanging from the ceiling – the vase exerts a force on the hook attached to the ceiling, equal to its weight force. The hook, in turn, exerts an equal force on the vessel's chain, supporting it.
4 – hammer in nail – the hammer exerts a force on the nail, causing it to penetrate the wood. The nail, in turn, exerts a force on the hammer.
By Domitiano Marques
Graduated in Physics
Source: Brazil School - https://brasilescola.uol.com.br/fisica/exemplos-pares-forca-acao-reacao.htm
