There are many demonstrations that show resonance in dramatic ways:

1.           One is to use a margarita glass filled with some water and rubbing your finger around the rim. 

2.         If you have two similar tuning forks attached to resonance boxes, you can strike one of them that is facing the other.  Deaden the struck fork and you should hear the other one ring slightly.

3.         The most dramatic involves a fissure-burner and a large tube, made of either PVC or thick card board.  Igniting the fissure-burner will force air upward.  You can then place the tube around the flame and adjust the “height” of the air-column until resonance is reached.  With the right tube, the classroom could shake!

On the subject of resonance, it should be noted that resonance is an over-simplified explanation of the Tacoma Narrows Bridge collapse.  The phenomenon is actually known as “aeroelastic flutter.”  I have only recently read about this and I still do not fully understand the topic and am currently at a complete loss as to how I can try to explain it to high school students.  Nonetheless, considering an article on this subject came out in 1990; I think it is about time that we physics teachers at least mention that there was more than resonance due to vortex shedding that led to the bridge’s demise.

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