Inertial Reference Systems

Possessing initial data, for any moving body it is possible to calculate the value of its acceleration, velocity, location (coordinates), etc. All such calculations are performed within the kinematics. However, this section of science does not study the very processes that arise during mechanical movement. To answer questions about the characteristics of motion, the reason for the acceleration pulse can be dynamics.

We take boxes with one match inside and start moving it on the table in the same direction with the same speed. What happens to the match? Does it rest or move? It all depends on what frame of reference we choose the main one. In relation to the box, the match is at rest, but if you look at what is happening from the side (for example, the same table), it moves. The common thing in both cases is that the speed of the match is constant. To change it, you need to exert an external influence on the box and match, for example, push it off the table. It is this that characterizes inertial frames of reference. Suppose we are in a box next to a match. Since the external action is not obvious, at the moment of the fall you might think that the match itself has moved, gaining the momentum of acceleration. But if you look at what is happening, being on the table, then the behavior of the match is easily explained by the change in the speed of movement of the box. In fact, we have described inertial and non-inertial frames of reference. For the first, the action of external forces is characteristic, and for the latter, the resulting acceleration by external forces can not be explained. In this example, inertial reference frames are connected to the table surface and any other object outside the box, since it is obviously an external effect on the object under study. The problem of reference frames was of interest to such prominent scientists of antiquity as Galileo and Aristotle. Only in the 17th century I. Newton on the basis of their works formulated his first rule of inertia, better known as Newton's First Law.

It says that the existence of such reference frames is admissible, under which there is no external impact on the body from other bodies, and the speed of motion does not change either in value or in direction. If there are several effects, but they are balanced, then the same rule that uses inertial reference frames (ISO) operates. If we consider one reference frame relative to the other, with the module and velocity constant, then we can state that there is a huge amount of ISO in nature. Consequently, inertial frames of reference surround us everywhere.

It is much easier to understand Newton's First Law if one understands the conclusions of his predecessors - Aristotle and Galileo.

Aristotle argued that if the body does not have any outside influence, then its natural state is peace. In the case of moving the body at a constant speed, an external force must be present.

Galileo supplemented these conclusions: the absence of external influence does not mean that the body can not move evenly and without changing direction. The very force that exerts an effect is wasted on compensating for attraction, friction, etc.

The inertial system is completely based on the First Law, according to which any body rests or moves evenly, until the external force changes its state. An important feature: this law can not be performed in all possible frames of reference.

The inertial system is brilliantly confirmed and actively used in celestial mechanics and cosmonautics (heliocentric system). It should be noted that there is no such reference frame that would be inertial for all possible processes of the system under consideration.