This is a recording of a recent live teleclass I did with thousands of kids from all over the world. I’ve included it here so you can participate and learn, too!


Sound is a form of energy, and is caused by something vibrating. So what is moving to make sound energy?


Molecules. Molecules are vibrating back and forth at fairly high rates of speed, creating waves. Energy moves from place to place by waves. Sound energy moves by longitudinal waves (the waves that are like a slinky). The molecules vibrate back and forth, crashing into the molecules next to them, causing them to vibrate, and so on and so forth. All sounds come from vibrations.


Materials:


  • 1 tongue-depressor size popsicle stick
  • Three 3″ x 1/4″ rubber bands
  • 2 index cards
  • 3 feet of string (or yarn)
  • scissors
  • tape or hot glue

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What’s Going On?

Do you remember where all waves come from? Vibrating particles. Waves come from vibrating particles and are made up of vibrating particles.


Here’s rule one when it comes to waves…. the waves move, the particles don’t. The wave moves from place to place. The wave carries the energy from place to place. The particles however, stay put. Here’s a couple of examples to keep in mind.


If you’ve ever seen a crowd of people do the ‘wave’ in the stands of a sporting event you may have noticed that the people only vibrated up and down. They did not move along the wave. The wave, however, moved through the stands.


Another example would be a duck floating on a wavy lake. The duck is moving up and down (vibrating) just like the water particles but he is not moving with the waves. The waves move but the particles don’t. When I talk to you, the vibrating air molecules that made the sound in my mouth do not travel across the room into your ears. (Which is especially handy if I’ve just eaten an onion sandwich!) The energy from my mouth is moved, by waves, across the room.


Questions to Ask

  • Does the shape of the index card matter?
  • What happens if you change the number of rubber bands?
  • What if you use a different thickness rubber band?
  • What happens if you make the string longer or shorter?
  • can you make a double by stacking two together?
  • Can you get a second or third harmonic by swinging it around faster?
  • Why do you need the index card at all?

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Comments

6 Responses to “Special Science Teleclass: Sonic Vibrations”

  1. Aurora Lipper says:

    This is the Tacoma Narrows Bridge in the state of Washington.

  2. How do you spell the name of the bridge? I’m trying to find some photos of it from back in the day.

  3. Aurora Lipper says:

    The bridge collapsed because the vibrations moved back and forth through the structure and increased in strength. This is called resonance.
    The frame of skyscrapers is made from steel columns that are designed to flex a little bit. The concrete is mounted to to the steel in sections so it won’t crack.
    The friction of the tires on the car are keeping it in place. But eventually the car would have moved.
    They recorded the bridge and water from different cameras on the shore.
    Yes, it is surprising to see people just walking. They didn’t understand that they were in danger.

  4. If not even a single tree fell over, how did the bridge fall down? And if concrete was built to make sky scrapers, then how did the concrete move so big side to side? And how can the car not be moving with the bridge twisting? 2 years ago, we had like 60-80km winds and our massive, very heavy trampoline didn’t even move! And back then, they didn’t have drones and it was to windy to take a boat on the water. So how did the get the footage from on the water and in the air? The guy on the bridge didn’t even look like he was running away, he didn’t even look scared!

    Please get back to me about what you think:)

  5. Yes you’re right – this is a live class I did with a lot of students, which ended with a hands-on activity. We do have many printables with the classes, this is one we don’t currently have one for. A more current class (including a printed review sheet) is found here: https://www.sciencelearningspace.com/science-with-aurora/september-physics-2021/#week8 and the button near the top of the page (red-brown color) is the printable for the entire month of physics.

  6. alicia_lister says:

    Would it be possible to create a printable instruction sheet for this activity in the future?
    For others – the activity begins at 31:29 in the video.