Before you begin to get acquainted with the phenomena of resonance, you should study the physical terms associated with it. There are not many of them, so remembering and understanding their meaning will not be difficult. So, first things first.
What is the amplitude and frequency of movement?
Imagine an ordinary yard where a child sits on a swing and waves his legs to swing. At the moment when he manages to swing the swing and they achieve uniform movement from one side to the other, you can calculate the amplitude and frequency of movement.
Amplitude is the longest deviation from the point where the body was in equilibrium. If we take our example of a swing, then the amplitude can be considered the highest point to which the child swung.
And the frequency is the number of oscillations or oscillatory movements per unit time. The frequency is measured in Hertz (1 Hz = 1 oscillation per second). Let us return to our swing: if a child passes only half of the entire swing length in 1 second, then its frequency will be 0.5 Hz.
How is frequency related to resonance?
We have already found out that the frequency characterizes the number of oscillations of an object in one second. Imagine now that a weakly swinging child an adult helps to swing, pushing the swing over and over again. Moreover, 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 swing swing. That is, an external force (in this case, shocks) will not contribute to enhancing the oscillation of the system.
If the frequency with which the adult sways the child is numerically equal to the frequency of the swing, the resonance may occur. In other words, an example of resonance is the coincidence of the frequency of the system itself with the frequency of the forced oscillations. It is logical to imagine that the frequency of forced oscillations and resonance are interconnected.
Where can I see an example of resonance?
It is important to understand that examples of the manifestation of resonance are found in almost all areas of physics, ranging 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 resonance example will provide insight. Suppose you are walking along a thin board thrown across a river. When the frequency of your steps coincides with the frequency or period of the entire system (board-person), 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 oscillation amplitude of the board, which goes beyond the permissible value of the system and this will ultimately lead to inevitable breakdown of the bridge.
There are also those areas of physics where you can use the phenomenon of useful resonance. Examples may surprise you, because usually we use it intuitively, without even realizing the scientific side of the issue. So, for example, we use resonance when we try to get the car out of the pit. Remember, it is easiest to achieve a result only when you push the car at the moment it moves forward. This example of resonance enhances the amplitude of motion, thereby helping to pull the machine out.
Examples of harmful resonance
It is difficult to say which resonance occurs more in our lives: good or harming us. History knows a considerable number of terrifying consequences of the resonance phenomenon. Here are the most famous events where you can observe an example of resonance.
- In France, in the city of Angers, in 1750 a detachment of soldiers walked in foot over a 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, and the bridge collapsed into the river.
- There were times when a house was destroyed in the villages due to a truck driving along the main road.
As you can see, resonance can have very dangerous consequences, which is why engineers should carefully study the properties of building objects and correctly calculate their vibration frequencies.
Useful Resonance
Resonance is not limited to only dire consequences. With a careful study of the world around you can observe a lot of good and beneficial resonance results for humans. Here is one striking example of resonance, which allows people to receive 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 vibration frequencies are transmitted from the upper deck to the lower. When a lutier leads a bow along a string, the latter, like an arrow, defeats the friction of the rosin surface with its elastic force and flies in the opposite direction (starts moving in the opposite region). There is a resonance that is transmitted to the case. And inside it there are special holes - ephs through which resonance is brought out. This is how it is controlled in many stringed instruments (guitar, harp, cello, etc.).