Resonance: Earthquakes to Pasta
Have you ever wondered what causes buildings to crumble during an earthquake? Try modeling this occurrence with noodles and bread to see what happens!
What You Need
- Three pieces of long, dry pasta noodles
- Pieces of Bread
What to Do
1. Break the pasta noodles off into three different lengths: 6 inches, 5 inches, and 4 inches.
2. Tear off a small piece of bread and stick it on the top of each of the pasta noodles to add weight.
3. Hold all three sticks in one hand with the bottoms of the pasta even in your hand.
4. Slowly shake your hand back and forth.
5. Notice that only one of the pasta noodles oscillates.
6. Increase the speed at which you shake your hand.
7. Notice the original pasta noodle stopped moving and the next one is now oscillating.
8. Increase the speed once more to see the last noodle start to oscillate while the other noodles stay still.
Below you can see how the noodles move when you vary the speed of your hand shaking (the frequency).
What's Going On?
In a general sense, frequency means how many times something happens in one second. Here, we are moving our hands back and forth, causing our pasta and bread concoction to rock back and forth. In this case, frequency measures how often the pasta noodles complete one full swing.
You begin with a very low frequency by shaking your hand back and forth slowly. The tallest noodle will begin to oscillate with the lowest frequency, and the shortest noodle requires the highest frequency to oscillate.
When shaken at their resonance frequencies, objects will oscillate with larger amplitudes (bigger swings) than at other frequencies. The noodles shake more because the frequency at which you move your hands approaches the resonant frequency of the noodle at that length.
You can see how the oscillations change in the video below.
If you think of the pasta noodles as buildings and your hand moving as an earthquake you can see that the taller buildings take less of movement to shake, and the smaller buildings take a much higher frequency oscillation to shake. If you increase the frequency at which you shake your hand enough the noodles will break.