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?

Day 9: Can We Try That?

Thursday, 25 August 2016

I showed this:

and the kids asked if they could try it. Sure, why not? Here’s the 50th attempt at constructive interference:

Turns out it’s tough to get the timing right. But dang, the kids sure do keep at it. (BTW, the destructive interference isn’t nearly as engaging.)


Day 8: Improving the Lab Experience

Wednesday, 24 August 2016

So I asked my department chair to observe me (only to discover that Robert Kaplinsky invented #ObserveMe  (blog post) a few hours earlier) because I wanted feedback on how I run a lab.

Oh and also, ever since the Great Slangle Fest of 2016, I was unwilling to give that class a bunch of slinkys. So I morphed the lab into something like a lecture with lots of Notice & Wondering, which I was completely happy with.

Now, to the class: After playing with constructive interference, I set the entire class up with a question, “what do you think will happen if the people at both end of this slinky make pulses on opposite sides of the slinky?”

We tried it at full speed. Couldn’t tell what we were seeing. Then one kid asked if he could film it in slow motion. HE ASKED IF HE COULD FILM SCIENCE. ❤ ❤ ❤

Class went on like this all period. We learned all about reflection, transmission, and interference. My cycle looked like this:

  • I pose a question,
  • they make a conjecture,
  • they make an observation(s)

By the way, the physical setup was awesome: kids in a circle, slinky stretched across the diameter. Every time we changed a thing, I had kids pass the slinky to their right.

Here’s that key moment (next time I’ll go for better contrast):

Screen Shot 2016-08-25 at 9.32.58 PM

It’s just a screengrab — don’t go clicking and expecting it to play.

After the lesson, I dismissed the kids 5 minutes early and spoke with my chair. We brainstormed some ideas (a lab quiz, some tweaks to my current setup, focusing on the students developing experiments to name a few) and I feel now like I have ideas to play around with.

This is all to say, this kind of observation is powerful because the observer has a non-threatening goal — to help me improve. I recommend getting in on this #ObserveMe thing, it might just change your world!


Day 5: What Makes a Good Lab Writeup?

Friday, 19 August 2016

Find the speed of a wave traveling through a slinky. Take whatever materials you need but I won’t tell you how to do it. Here’s what two students said they were going to do:


3/4 of this description could work with literally any lab.


I like how this kid focused on what they were measuring. 

Two questions come to mind:

  • how can I model good diagramming of experiments?
  • how can I help these kids explain the procedure they just did (like, they know when they started the timer and when they stopped — this description just doesn’t capture it)?

Disclaimer: I studied math ed, not science ed and as such, have a huge case of imposter syndrome going on when it comes to labs. Cause y’all took courses in this stuff, right?


In middle school, my students were taught to write a procedure for a science experiment. There was heavy focus on enumerated lists that start with “gather materials”. I prefer to see the kids’ methods — what did you choose to measure/calculate and why do you think that’s the right choice?

The shift from procedures to methods is huge for 9th graders!

So I made up an example to show my kids. For distances, sketch out where you’re measuring. For times, tell me when you’ll start and stop the timer. I’d also like to see a little explanation of why you chose to do what you did.


Here’s what I like to see, kids.

What would happen if I put the methods section at the end of the lab? Maybe kids would be able to better word what they did after they’ve done it a few times. It’s worth a shot.


Student diagrams almost always suck on this lab. I think they view the diagrams as busy work. I clearly haven’t sold the students on the value a diagram can provide.

Meh, I want to hit publish, but have more to say about diagrams. Maybe another time. Have a great day, friends!


Day 3: Slangles

Wednesday, 17 August 2016


The kiddos in 4th period calculated the speed of a wave traveling through a slinky. Some of them even discovered longitudinal waves in the process. Other groups created tangled messes (see above and credit to @physicsbjork for the portmanteau ‘slangles’), sigh.

One change this year: I divided up longer labs so that they would fit in a single class period. My thinking is that, at least at the beginning of the year, kids were stressed when I’d hand them a multi-day lab, I had trouble pacing the lab, and we weren’t reflecting on the parts of a lab as well as I wanted. I figure that since I was good at circling up with kids at the end of a lab, I’d just create artificial lab endings by having more. Here are two parts that used to be one:

This is my 4th year doing the daily blog thing.

  • Day 3 from 2015 (where I featured more pictures from students, a practice I forgot about but want to return to)
  • Day 3 from 2014 (where I focused on building vocabulary)
  • Day 3 from 2013 (where I wrote about challenging kids to make waves travel faster through a slinky — something I did today as well)

I’ve been teaching the same course this whole time. How do y’all keep it up?

Day 2: Getting the Slinkys Out

Tuesday, 16 August 2016

So yesterday was the first day of school which consisted of 35 minute classes, a pep rally, and picnic lunch. I didn’t take a single picture all day long.

Today was better (from a documentation standpoint).


Beginning of year 5 in this place and year 13 overall.

Before I taught any kids, I had the chance to work with my daughter and a friend (both students at Georgia Tech) on an Arduino project that I may use in my JanTerm Maker class. It’s an LED cube like this:

We got one cube assembled and tested in a little over an hour. I’m excited to get the Arduino circuit hooked up tomorrow.

Last year’s electronics/Arduino project was over their heads, so I’ve been searching for a better option. So far, this looks like a great replacement for the 9th and 10th graders to build.

Then some kids showed up for class.


Finally, I assigned some reading from Physics Classroom for homework. I stressed that they’re to read and answer a few conceptual questions in no more than half an hour. Fingers crossed that my new homework system works out.