Having initial data for anymoving body can calculate the value of its acceleration, speed, location (coordinates), etc. All such calculations are performed in the framework of kinematics. However, this section of science does not study the processes that occur during mechanical movement. Answer questions about the characteristics of motion, the cause of the acceleration pulse can dynamics.
Take a box with one match inside and startmove it across the table in the same direction at the same speed. What happens to the match? Is she resting or moving? It all depends on which frame we choose the main one. With respect to the box, the match rests, but if you look at what is happening from the side (for example, the same table), it moves. The common in both cases is that the speed of the match is constant. To change it, it is necessary to exert an external influence on the box and the match, for example, push it off the table. This is what characterizes inertial reference systems. Suppose we are in a box next to a match. Since the external impact is not obvious, then at the moment of the fall one might think that the match itself was set in motion by acquiring an acceleration impulse. But if you look at what is happening, being on the table, then the behavior of a match is easily explained by a change in the speed of movement of the box. In fact, we described inertial and non-inertial reference systems. For the former, the action of external forces is characteristic, and for the latter, the resulting acceleration by external forces cannot be explained. In this example, inertial reference systems are associated with the surface of the table and any other object outside the box, since the external effect on the object being studied is obvious. Such prominent scholars of antiquity as Galileo and Aristotle were interested in the problem of reference systems. It was only in the 17th century that I. Newton formulated his first rule of inertia, better known as Newton's First Law, on the basis of their work.
It states that the existence of suchreference systems in which the body is not externally influenced by other bodies, and the speed of movement does not change either in meaning or direction. If there are several impacts, but they are balanced, then the same rule that inertial reference systems (ISO) apply. If we consider one reference system relative to another, with the modulus and speed value unchanged, then it can be argued that in nature there is a huge amount of ISO. Consequently, inertial reference systems surround us everywhere.
It is much easier to understand the First Law of Newton, if you read the conclusions of his predecessors - Aristotle and Galileo.
Aristotle argued that if the body does notit turns out to be of any third-party influence, then its natural state is peace. In the case of moving the body at a constant speed, external force must be present.
Galileo added these conclusions:the absence of external influence does not mean at all that the body cannot move evenly and without a change in direction. The very force that has an effect is wasted on compensation of attraction, friction, etc.
Inertial system is completely based on Firstaccording to the law, according to which any body is at rest or evenly moving, until an external force changes its state. An important feature: this law can be implemented not in all possible reference systems.
Inertial system is brilliantly confirmed andIt is actively used in celestial mechanics and cosmonautics (heliocentric system). It should be noted that there is no such reference system that would be inertial for all possible processes of the system under consideration.
