Have you ever observed the phenomenon of resonance at home or on the street?

Yes, I had to. For example, a backpack hangs on a hook in a train carriage. When the natural vibration frequency of the backpack coincides with the frequency of the car hitting the rail joints, the backpack begins to swing.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.