What are some examples of resonance?
The Tacoma Narrows bridge collapse.
The Tacoma Narrows bridge collapse is a classic example of the destructive potential of resonance:
The wind provided a driving/forcing frequency that matched one of the bridge's modes of vibration (i.e. natural frequency). If you look carefully you can see something like a standing wave set up on the bridge.
A couple of examples the good uses of resonance:
1. The use of ultrasound to break up gall stones. The frequency of the ultrasound matches the natural frequency causing maximum transfer of energy and the large amplitude of oscillation breaks up the stone.
2. Microwaves in microwave ovens have a frequency equal to the the natural frequency of water molecules. The molecules are oscillated and gain kinetic energy raising the temperature of the food.