# Day 12: Standing Waves

Tuesday, 30 August 2016

I teach three sections, so today the third section of physics saw the standing wave setup. I encouraged kids to film in slo-mo and project on the board. We saw some great wave action (as long as the wave frequency was under about 30 Hz, that is).

Then I gave them the giant springs and asked them to make standing waves in the fundamental frequency, 2nd harmonic, and 3rd harmonic. Some had timing issues but all got the idea:

Afterwards, we developed the mathematical pattern for standing waves on a string (L=nλ/2). Finally, the kids worked on a classwork assignment to practice with these problems.

During planning, my colleague and I played with the solar cars we built last week. We hope to implement this as a build project when we study electrical circuits. I also imagine reusing the cars when we study mechanics.

Build time: maybe 60 minutes for students in a class?

Tools: soldering iron, xacto knife, hammer, glue (not really a tool?)

Experiment opportunities:

• how does solar panel voltage (or current?) output vary with light source angle?
• how does wheel RPM vary with % of panel exposed to light?
• how does vehicle speed vary with weight?
• what’s the best gearing setup? (wheel comes with 2 gears we didn’t use)

What would you do with this kit?