Mechanics

# Strength and movement

In the History of Science, there have been many discussions about movement and its relationship with force. Today we understand that the force is related to the variation of the velocity.

The explanations of the phenomena of nature occur through the understanding we have about what we observe. Many theories considered correct in the past were later reworked, as scientific truths are dated and depend on science itself to be validated and/or refuted. So it was with the ideas related to force and motion .

The relationship between force and motion generated numerous discussions in the History of Science and was the focus of attention of many scholars, such as Aristotle and Galileo Galilei .

For Aristotle , force was linked to the existence of speed. It was impossible, according to him, for the existence of a movement in which there was no continuous action of a force. The movements, according to the Aristotelian perspective, can be natural, when the body seeks its natural place in the universe (hypothesis used to explain the fall of bodies ), and violent, when bodies are removed from their place of origin through the application of a force. In his work entitled Mechanics, Aristotle stated that a body in motion would only come to immobility if the force acting on it ceased to act. Therefore, we can understand that, according to this view, there is only velocity if there is a force.

In the 14th century, the French priest Jean Buridan proposed a new explanation for the question of movements, introducing the concept of impetus . For Buridan, a force applied to an object transfers an impetus to it. Thus, velocity lasts as long as the momentum of force exists.

Clarity in the explanations of the question of movements began to emerge with Galileo Galilei in the 17th century. For Galileo, an object in motion, after being propelled by a force, only stops due to the action of external forces, such as friction . If there was the possibility of totally eliminating friction, the body would be in perpetual motion without the action of forces on it. For Galileo, forces are not related to velocity itself, but to its variation.

The philosopher René Descartes , a contemporary of Galileo, realized that the rectilinear trajectory is a consequence of the lack of application of a force and stated that motion can occur without the action of forces for any bodies, including celestial bodies.

In the 17th century, Isaac Newton published the work Mathematical Principles of Natural Philosophy, in which the concept of inertia was exposed and the relationship between force and motion clarified. Newton wrote:

“ An impressed force is an action exerted on a body in order to change its state, either at rest or in uniform forward motion in a straight line.
This force consists only in action; and no longer remains in the body when the action ends…”

We conclude that forces can act on bodies by increasing or decreasing their speed. In the case of uniform rectilinear motion , the velocity of a mobile is maintained without the action of external forces.