Astronomy: We’re currently learning about light and the electromagnetic spectrum. Which is why this tweet from Alom Shaha over the Thanksgiving weekend couldn’t have been more perfectly timed:
So on Sunday, I got a pack of 75 kebab skewers, 3 boxes of Dots candy (~150 Dots), and some tape:
And today I had the students assemble our own wave machine:
The skewers were spaced 10 cm apart and the whole machine spanned almost 24 feet. Here it is in action:
- Use duct tape. The tape needs to be under A LOT of tension. Weaker tape will just rip.
- Buy an extra box of candy. We would’ve had about 5-10 more sticks if kids didn’t sneak a few candies to eat.
- Put an extra layer of tape over the duct tape. (Non-duct tape is fine.) It keeps the skewers from sliding off at large amplitudes.
College-Prep Physics: A student project investigating the relationship between the rotational speed of a whirly tube and the pitch produced. The student used a Vernier microphone and Logger Pro to produce an FFT graph which indicated the pitch of the note produced. The student used the video camera on her iPhone to record the twirling so she could get an accurate number for the rotational speed in RPMs.
You can read more about the physics of whirly tubes here: http://www.exo.net/~pauld/summer_institute/summer_day13music/Whirly.html
College-Prep Physics: A student project examining how volume varies with distance. Is it inverse square like light and gravity? Is it different in different media? The student used a Casio keyboard to play a sustained note and used a Vernier sound meter to measure decibel levels at various distances. To test a different medium, the student used to cups connected by string, and used various length of string between the cups.
The sound using the cups and string was always louder than in air at the same distance, but it didn’t drop off in the same way as in air. We wonder whether the tension in the string might have something to do with it. Our reasoning being, if the string is more taught, the sound travels faster through the string and reaches the end with less decrease in amplitude, and therefore would sound louder. It is likely that the tension in string wasn’t held constant for different length string.
AP Physics C: We watched the NOVA special Fractals: Hunting the Hidden Dimension. There were a lot a parallels between what the mathematicians where saying and the themes in Arcadia. Mandelbrot is a main focus of the special, along with applications of fractals — from CGI special effects to antennas to fashion. Minds were blown.
As a bonus, we looked at select scenes from Stoppard’s Rosencrantz and Guildenstern are Dead. Again, Stoppard shows a knack for mixing science and humor:
College-Prep Physics: Students began work on WebAssign problems about waves.
Conceptual Physics: Students wrapped-up work on the bike light presentations.
AP Physics C: We finished reading Arcadia and began exploring the (sometimes chaotic, sometimes predictable) behavior of a simple logistic equation for modeling animal populations. The handout is here: Valentine’s Grouse: An Exploration of Chaos in Populations. And you can explore it yourself using my version of the population program in GlowScript.
College-Prep Physics: Wrapped up the wave/buggy lab from yesterday. We determined the model for our data to be wavelength = speed / frequency.
Conceptual Physics: Students finished building/testing their bike circuits and began drawing and annotating their final circuit diagrams.
College-Prep Physics: Used the long slinky to generate discussion about how we might make the waves travel faster down the slinky. That lead into a dissucssion about frequency, wavelength, wave source, and wave medium. Then students used constant speed buggies, adding machine tape, markers, rulers, and a metronome app on their phones to experimentally determine the relationship between frequency and wavelength. (Sorry, I’m reposting the video from last year.) Also showed this I Love Lucy clip:
Conceptual Physics: Students finished building and testing their modified bike light circuits and began making their final annotated circuit diagrams.
AP Physics C: All but one student was taking the AP Macroeconomics exam today. We’ll finish reading Arcadia tomorrow.