What is dynamics?

We explain what dynamics is and what are the fundamental laws of dynamics. History of discovery, and related principles.

1. What is dynamics?

The  dynamics is the part of physics that studies the relationship existing between the forces acting on a body and the effects that will occur on the movement of that body.

Ancient Greek thinkers believed that the speed and constancy of movement in the straight line of a body (phenomenon described years later as uniform rectilinear motion or MRU) were proportionally related to a constant force. By extension, it was believed that the fall of a body belonged to that category, so the body that was heavier was supposed to fall faster . Then, Galileo Galilei understood that the fall of the bodies could not be a uniform movement, and that from the same height, two bodies of different weight take the same time to fall

. This context was what made it possible that some years later, Isaac Newton established the three fundamental laws of dynamics, which explained the fundamental patterns of body behavior.

2. Newton’s laws

• The principle of inertia . It indicates that when a body is at rest, or describes a movement of the characteristics of MRU, the forces that are applied on it have a null result. Care must be taken in this case, as they influence, for example, the friction force. When the forces are really balanced, the MRU can occur.
• The force is equal to the mass by the acceleration. This is the fundamental formula of dynamics, and comes from assuming a body at rest on a horizontal surface, which is subject to a force parallel to that surface, being able to do without friction: we will see that the body is set in motion at a constant acceleration If another force of greater intensity is applied, the acceleration will vary proportionally.
  In this way, this formula is reached, and the international unit of force, Newton (N), defined as the force that drives a mass of one kilogram with an acceleration of one meter per second squared can be established.
• Law of action and reaction. Whenever a body exerts a force on another, this second exerts an opposite of equal intensity and direction but opposite direction on the first. The first example is that of a body that weighs on a surface, which will receive from it the action of a force that opposes that of attraction that the earth exerts on it.

These laws are the fundamental laws of dynamics, which apply primarily to uniform rectilinear motion. However, there is also a dynamic of the circular movement , which happens when the force that is applied to a body in constant modulus can be maintained, perpendicular to the direction of movement. This occurs, for example, in the case of the constant force of attraction of the Sun on a planet, which prevents it from exerting a rectilinear movement instead of the orbit.

However, there is also the analysis of the behaviors of bodies when various particles intervene , in addition to the forces mentioned. The part of physics that uses statistical methods to study the overall behavior of systems is thermodynamics.

It has a series of principles, among which we can mention the thermal equilibrium , that is, the equality between the heat received and that emitted by the body, achieved through heat exchange. It is also said that the energy is not produced or destroyed , but that it is transformed, making it impossible to produce work without energy consumption , and from that it emerges that heat cannot be completely transformed into work, there is always a loss.

There is also a colloquial use of the term, which is applied to speak symbolically of things that are in motion . You can talk about the dynamics of political processes , public events or anything, to refer to ‘how it developed’ for a period of time . Also, it is used as an adjective to talk about people who are very restless and spend a lot of time moving.