In the development of natural science, the leading role has been and still is played by classical mechanics, or Newtonian mechanics . An explanation of many physical phenomena and processes taking place in terrestrial and extraterrestrial conditions fits into its framework. Many research methods are formed on its basis. The essence of the mechanistic worldview that prevailed in science almost until the beginning of the twentieth century is reduced to an explanation of all physical processes by the movement and interaction of bodies and particles. That is, mechanics is the science of the motion of bodies.
Newton's concept, briefly expressed by Einstein, said: physical reality is determined by factors of time, space, material point and force, i.e., the interaction of material points. The main task of mechanics, thus, was reduced to the study of physical events, which was understood as the movement and interaction in the space of material points that occurs according to unchanged laws.
In the modern interpretation, the field of application of classical mechanics is the interaction of bodies with relatively slow motion (many times less than the speed of light). The "classical" concepts of space, time, force, mass, etc. remained unchanged, the basic laws of mechanics operate and will not be refuted as long as science exists.
Let's remember the main concepts of mechanics. This is a mechanical movement - the so-called change in the position of a given body relative to other bodies in space and time (an example is the movement of a transport, clockwise, celestial body, molecule), relativity of movement - a body moves relative to some bodies and can be motionless relative to others . Example - a car driver moves relative to pedestrians and is stationary relative to the car body. Therefore, there is the concept of a reference body - this is the name of the body relative to which the movement occurs.
The coordinate system determines the location of a body or point in space. Movement can occur in a straight line, in a plane or in space. Accordingly, one, two or three of its coordinates change. The main task of mechanics is to determine the coordinates of the body at a certain (any) moment. In this case, the coordinate refers to the distance from the reference point along the corresponding axis. In addition, it should be borne in mind that the movement is carried out in a certain time period, i.e., time is also one of the initial values.
Thus, the reference frame, in which the main task of mechanics is solved, is composed of the coordinate system and the clock. Any movement does not occur on its own, but relative to the frame of reference that we have chosen. Knowing how the coordinate of a body changes in time, we can find out the position of a given body (point) at any moment we need.
The main task of mechanics is thus reduced to determining the position of the body (its coordinates) at any moment we need.
Each body has its own specific dimensions. With translational motion, all of its points move along one trajectory, and there is no need to describe the motion of all points. How to determine its coordinates? Under certain conditions (if the dimensions of the body are many times smaller than the distance traveled by it), its dimensions can be neglected and the body considered a material point. For example, when the Earth moves in orbit, our planet can be mistaken for a material point. When studying the processes occurring on the surface of the Earth, it can not be considered as such. That is, in mechanics, by a material point is meant a body, the dimensions of which can be neglected.
A path is the distance that a point travels along a path. Displacement is a vector (directed segment) connecting two positions of the body, the initial and the final.
In addition, movement is not always translational. If parts of the body move along different trajectories, such a movement can be considered as rotation around a certain axis. Any movement in mechanics is a combination of translational and rotational movements.