The best example of resonance, explaining its essence

Before getting acquainted with the phenomena of resonance, it is necessary to study the physical terms associated with it. They are not so many, so remember and understand their meaning will not be difficult. So, about everything in order.

What is the amplitude and frequency of motion?

Imagine an ordinary courtyard where a child is sitting on a swing and waving legs to swing. At a time when he manages to swing the swings and they reach a uniform motion from one side to the other, you can calculate the amplitude and frequency of motion.

Amplitude is the greatest length of deviation from the point where the body was in the equilibrium position. If we take our example of a swing, then the amplitude can be considered the highest point to which the child was swinging.

And the frequency is the number of oscillations or vibrational movements per unit time. The frequency in Hertz is measured (1 Hz = 1 oscillation per second). Let's return to our swing: if the child passes only one half of the entire length of the swing in 1 second, its frequency will be 0.5 Hz.

How is the frequency associated with the phenomenon of resonance?

We have already found out that the frequency characterizes the number of oscillations of the object in one second. Imagine now that a weakly rocking child, an adult man helps to swing, over and over again pushing a swing. In this case, these shocks also have their own frequency, which will increase or decrease the swing amplitude of the "swing-child" system.

Suppose an adult pushes a swing at a time when they are moving towards him, in which case the frequency will not increase the amplitude of the movement of the hanging swings. That is, the external force (in this case, the tremors) will not contribute to increasing the oscillation of the system.

If the frequency with which an adult shakes a child is numerically equal to the very frequency of the swing, a resonance may occur. In other words, an example of resonance is the coincidence of the frequency of the system itself with the frequency of forced oscillations. It is logical to imagine that the frequency of forced oscillations and resonance are interrelated.

Where can you see an example of resonance?

It is important to understand that examples of the manifestation of resonance are found practically in all areas of physics, from sound waves to electricity. The meaning of resonance is that when the frequency of the driving force is equal to the natural frequency of the system, then at this moment the amplitude of the oscillations reaches the highest value.

The following example of resonance will give an insight into the essence. Suppose you walk on a thin board, thrown across the river. When the frequency of your steps coincides with the frequency or period of the whole system (a human board), then the board begins to fluctuate strongly (bend down and up). If you continue to move in the same steps, the resonance will cause a strong fluctuation amplitude of the board, which is beyond the permissible value of the system and this will eventually lead to inevitable breakage of the bridge.

There are also those spheres of physics where it is possible to use such a phenomenon as useful resonance. Examples may surprise you, because usually we use it intuitively, without even guessing about the scientific side of the question. So, for example, we use resonance when we try to pull the car out of the pit. Remember, it is easiest to achieve the result only when you push the car at the moment of its movement forward. This example of resonance enhances the amplitude of the motion, thereby helping to pull the machine out.

Examples of harmful resonance

It is difficult to say which resonance in our life occurs more: good or harming us. There are a lot of horrifying consequences of the phenomenon of resonance. Here are the most famous events on which one can observe an example of resonance.

1. In France, in the city of Angera, in 1750 a detachment of soldiers walked in the foot through the chain bridge. When the frequency of their steps coincided with the frequency of free oscillations of the bridge, the amplitude of the oscillations (amplitude) increased sharply. There was a resonance, and the chains broke off, and the bridge collapsed into the river.
2. There were cases when in the villages the house was destroyed because of the passing truck on the main road.

As you can see, resonance can have very dangerous consequences, that's why engineers should carefully study the properties of building objects and correctly calculate their vibration frequencies.

Useful resonance

Resonance is not limited only to disastrous consequences. With careful study of the surrounding world, you can observe a lot of good and profitable results for a person. Here is one vivid example of resonance, which makes people enjoy aesthetic pleasure.

The device of many musical instruments works on the principle of resonance. Take the violin: the body and string form a single oscillatory system, inside which there is a pin. It is through it that the frequencies of oscillations from the upper deck to the lower one are transmitted. When the lyutier drives a bow along a string, the latter, like an arrow, overcomes its friction with the force of elasticity of the rosin surface and flies in the opposite direction (starts moving in the opposite direction). There is a resonance that is transmitted to the case. And inside it there are special holes - the efs, through which the resonance is output outside. This is how it is controlled in many stringed instruments (guitar, harp, cello, etc.).