William asks:

After voting for the LEGO® CUUSOO – Ladyada’s Workshop! project, I submitted this sine-wave-drawing gadget: http://lego.cuusoo.com/ideas/view/17603 . In the comments, @kiff9 wrote, “”I am having trouble understanding…. Could you explain in words that would make sense to a 13 year-old?””. I’m happy that kiff9 spoke up! I want to give a good answer and I’m seeking professional help :-).

So, my Ask-an-Educator question is: How do I explain this sine-wave-drawing contraption in words that would make sense to a 13 year-old?

Nice gadget! Very simple, yet effective.

As for explaining a sine wave to a 13 year old, I would start with a jump-rope. If two people stand apart holding a jump-rope (or any rope really) and one person begins to move the rope up and down so that it makes a complete 1-node standing wave. If the two people move closer together, while maintaining the complete wave, then you are increasing the amplitude and vice versa. Then if one person begins to move the rope up and down faster so that you make a 2-node standing wave, you have increased the frequency. Have them continue to see how many nodes they can make. Finally, if you wanted to you could have the two people walk in one direction while maintaining their wave and you have demonstrated a phase shift

Another way of to demo a sine wave is with a wave generator. This java app allows you to display and manipulate a mathematically based sine wave.

Good luck with your explanation and I hope I have helped!

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Lets say you have a wheel with a light on it and it is spinning at a constant rate but is at a right angle to you so you don’t see it as a circle but goung up and down, moving fastest near the center. Now move the wheel at a fixed speed in the direction of the axis of spin. It will trace out a sine wave.

I would suggest graphing the movement for them on graph paper.

Best simple example of a sine wave I’ve seen is MIT’s demo of simple harmonic oscillation: http://www.youtube.com/watch?v=P-Umre5Np_0 AKA the spring, spray paint, and rolling paper device.

A spirograph!