From the curriculum at school and institute, many learned the definition of resonance, as gradual or abrupt phenomena. increasing the amplitude of oscillations of a certain body when an external force is applied to it with a certain frequency However, few can answer practical examples of what resonance is.
- 1 Physical definition and binding to objects
- 2 Textbook example
- 3 Examples that repeat many
- 4 An example of the action of a constant force
- 5 Controlled application
Physical definition and binding to objects
Resonance, by definition, can be understood as fairly simple process:
- there is a body that is at rest or oscillating with a certain frequency and amplitude;
- external force acts on it with its own frequency;
- in the case when the frequency of the external action coincides with the natural frequency of the body in question, a gradual or sharp increase in the amplitude of oscillations occurs.
However, in practice, the phenomenon is considered as a much more complex system. In particular, the body can be represented not as a single object, but as a complex structure. Resonance occurs when the frequency of the external force coincides with the so-called total effective oscillatory frequency of the system.
Resonance, if viewed from the standpoint of physical definition, must necessarily lead to the destruction of the object. However, in practice there is the concept of the quality factor of an oscillatory system. Depending on its value, the resonance can lead to different effects:
- with a low Q-factor, the system is unable to largely sustain incoming oscillations. Therefore, there is a gradual increase in the amplitude of natural oscillations to the level when the resistance of materials or compounds does not lead to a stable state;
- high, close to unity, quality is the most dangerous environment in which resonance often leads to irreversible consequences. Among them can be both mechanical destruction of objects, and the release of a large amount of heat at levels that can lead to fire.
Also, resonance occurs not only under the action of an external oscillatory nature. The degree and nature of the reaction of the system, to a large extent, is responsible for the consequences of the action of forces directed from outside. Therefore, resonance can occur in a variety of cases.
The most common example that describes the phenomenon of resonance is the case when a company of soldiers was walking over a bridge and brought it down. From a physical point of view, this phenomenon is nothing supernatural. Keeping pace, soldiers caused fluctuationswhich coincided with the own effective vibrational frequency of the bridge system.
Many people laughed at this example, considering the phenomenon only theoretically possible. But the achievements of technical progress proved the theory.
In the network there is a real video of the behavior of the pedestrian bridge in New York, which is constantly swaying strongly and almost collapsed. The author of creation, which by its own mechanics confirms the theory, when resonance arises from the movement of people, even chaotic - French architect, author of the suspension bridge Viaduc Millau, buildings with the highest supporting in columns.
The engineer had to spend a lot of time and money to reduce the quality of the system pedestrian bridge to an acceptable level and to ensure that there is no significant fluctuations. An example of working on this project is an illustration of how the effects of resonance can be curbed in low-Q systems.
Examples that repeat many
Another example that even participates in anecdotes is the splitting of dishes with sound vibrations, from violin lessons and even singing. Unlike a company of soldiers, this example was repeatedly observed and even specially checked. Indeed, the resonance resulting from the coincidence of frequencies leads to the splitting of plates, glasses, cups and other dishes.
This is an example of the development of a process in a high-quality system. The materials from which the dishes are made are sufficiently elastic mediumin which oscillations propagate with small attenuations. The quality of such systems is very high, and although the frequency overlap is rather narrow, the resonance leads to a strong increase in amplitude, with the result that the material is destroyed.
An example of the action of a constant force
Another example where the destructive action was manifested is the Takomsky suspension bridge that collapsed. This case and the video of the wave-waving swaying of the structure are even recommended for viewing at the faculties of physics of universities, as the most textbook example of such a resonance phenomenon.
Destruction of a suspension bridge under the action of the wind is an illustration of how relatively constant force causes resonance. The following happens:
- a gust of wind deflects a part of the structure — an external force contributes to the occurrence of vibrations;
- during the reverse movement of the structure, the air resistance is not enough to damp the oscillation or reduce its amplitude;
- due to the elasticity of the system, a new movement begins, which strengthens the wind, continuing to blow in one direction.
This is an example of the behavior of a complex object, where the resonance develops against the background of high quality and considerable elasticity, under the influence of a constant force in one direction. Unfortunately, the Takomsky bridge is not the only example of structural collapse. Cases were observed and are observed throughout the world, including in Russia.
Resonance can be applied in controlled, well-defined conditions. Among all the many examples you can easily recall the radio antenna, even developed by amateurs. Here, the principle of resonance in energy absorption is applied. electromagnetic wave. Each system is designed for a separate frequency band in which it is most effective.
MRI systems use a different type of phenomenon - different absorption of vibrations by cells and structures of the human body. The process of nuclear magnetic resonance uses radiation of different frequencies. Resonance that occurs in tissues leads to easy recognition of specific structures. Changing the frequency, you can explore these or other areas, to solve various problems.