Device description:
Classic experience showing the phenomenon of resonance.
http://cngsystem.pl/pl/realizacja/rezonans-kladki/
Phenomenon:
Walking on the footbridge, we stimulate it to vibrate. If the deflection frequency is consistent with the natural frequency of the footbridge, then its deflections are large. The excitation frequency with the greatest deflection of the footbridge is called the resonant frequency.
How to perform an experiment?
Walk over the footbridge several times, each time taking your steps in a different rhythm. What are you watching?