Oscillatory processes are one of the most common phenomena in nature. Various fields of knowledge are involved in their research, primarily physics. To answer the question of which vibrations are called free, it should be taken into account that this category is the initial one in the study of the whole variety of vibrational phenomena that take place in nature.
The following types are distinguished, classified on the following grounds.
By their physical nature, mechanical, electromagnetic, and mixed vibrations are distinguished, combining the features of those already named.
According to the method of flow in the environment, vibrations are distinguished:
- forced, that is, those that are caused and occur under the influence of various kinds of external disturbances of the environments in which they occur. In this case, the condition for the periodicity of these disturbances must be observed;
- free vibrations, also called intrinsic vibrations, which are initiated by the internal properties of the system and which are characterized by mandatory damping when the action of internal forces ceases or decreases;
- self-oscillations - those which are characterized by the presence in the system of a certain potential (potential energy), which ensures oscillations. The main thing is that free oscillations differ from self-oscillations; the dependence of the amplitude is not on the initial initiating impulse of force, but on the characteristics of the physical system itself;
- parametric - these are vibrations that are formed when the oscillatory system is intentionally given any parameter that acts as a manifestation of the properties of the external environment;
- random vibrations are those in which the factors affecting the oscillatory process are random, not parametric in nature.
Summarizing these characteristics, we can conclude that, in the most general form, oscillations are repeated changes of a certain system relative to its equilibrium state with a certain periodicity. The most common areas of manifestation of vibrational processes in nature are mechanical phenomena, chemical, wave and electric, astronomical, electromagnetic and others. A common property of all types of vibrations, without exception , is that they are directly related to the energy transition - the conversion of one type of energy into another.
As already noted, the starting point in the study of the nature of vibrational processes is the study of their kind, such as free vibrations. Their main characteristics are the following parameters:
- amplitude (A) - the largest deviation of the system from its equilibrium state (most often, the average value indicator is used);
- period (T) - a certain period of time during which it is possible to fix the repetition of the states of the system;
- frequency of free oscillations (f) - the number of oscillations that the system performs in a certain unit of time. This parameter is measured in hertz (Hz).
The relationship of these parameters is reflected in the formula that characterizes free vibrations as a phenomenon. For different oscillatory systems, the parameters in this formula are included in various combinations, depending on which particular system is considered.
For example, in the simplest oscillatory circuit, the period and frequency are connected by the formula: f = 1 / T, it can be seen from it that the period and frequency are inverse values.
If we consider the free vibrations that occur in a system such as a statically fixed spring with a certain elasticity (k), then we should turn to Newton’s second law. With this in mind, the formula reflecting the properties of the considered oscillatory system will take the form: F = -kx. This suggests that if we neglect the values of the friction forces and take the mass as constant, then such a system will always oscillate with the same period, even at different amplitudes and initial conditions of their occurrence.