ThinkThankThunk

Dealing with the fear of being a boring teacher.

14

Physics II: The Extent to Which I Will Lesson Plan

[Wow, this post got out of hand. There’s physics lesson ideas if you scroll down. There’s blowhardy editorializing if you start at the beginning.]

I don’t really love the idea of a lesson plan. It’s kind of presumptuous, actually, it’s a lot presumptuous. You have no idea how long it will take anyone to learn anything (Thanks, Tae), and you really can’t say that instruction lasting 45-90 minutes is somehow the magic bullet for learning any given idea.

Instead, I think it’s much more helpful to think about learning as a series of forays into learning something. These may be separated by days, months, or years, but eventually the person achieves some useful level of understanding. This is the great joke of standardized testing.

Here’s my model for teaching physics:

  1. Play. Give them some materials, an idea, or whatever, and let them play with it. You should watch like a zookeeper watches the gibbons.
  2. Formalize the play. Give them a task based on the results of the play. Fix this. Is that always true? How many can you make? Is there a pattern…
  3. Direct Instruction. Show them how their formalization matches up with a commonly accepted model. This may be a book, pedia de la wiki, some expert, whatever. Do an exemplar problem.
  4. Ask a better question. Now that we have some agency with the material. Have the students build something or ask something that really throws a wrench or demands to be asked. Report these results on white boards.
  5. Practice, maybe. Now the students can choose to do practice to further precipitate the ideas. I let them choose from mountains of problems I have on my website. Do a couple of the most enjoyable problems with the class at the board.

A Quick Refresh?

Review units generally make me barf. Mostly because the idea of review means that the course before mine either didn’t do its job, or for some reason, the material you’re reviewing won’t be naturally motivated by what you’re going to do in the future. Since both of those cases are unacceptable, I generally take a deep-end-of-the-pool approach.

Why? Again, I want my students to take the bet and lose. High school isn’t about content, it’s about learning what it takes to get something done and practicing the feeling of getting-things-done-that-seemed-previously-impossible.In fact, recent research has indicated that motivation and study habits trump latent “intelligence” when it comes to students achieving and retaining.

The beauty of Physics II in high school, is that it’s a catch-all. These are my favorite kinds of courses, because it really allows the teacher and student to explore ideas for the sake of exploration.

I want to honor the fact that high school students are unconsciously saying, “Hey, maybe I like this, can you help me find it interesting?”

Which is in stark contrast to the what college students are secretly saying, which is, “Hey, I already like this, so I’ll tolerate whatever I have to in order to do it for a living.”

Wthout further ado, and in no particular order:

Optics:

soap iris 2

Soap Bubble on a baking sheet. Mixture was made with Dawn and high glycerin fancy soap. A cylinder of white paper surrounds the bubble and a shop light completes the cylinder.

This investigation is awesome. Generally I just show them the picture I took (above) and they’re off and running. Here are some more, which are way better than mine.

So, at first they will play. I limit that time until just the moment where it could become unproductive, and then we stop and write grants. I think the kids will want to change the light angle, or concentrations of the soap solution. They’ll measure the colors with a histogram tool in PhSh or GIMP. Who knows!

Ancillary optics projects: My students loved shooting lasers through reading glasses to figure out what their “power” ratings meant.

Also, set up some aquariums fill them with water and play with lasers. We set up an oil spill (last year’s Gulf issues) and had them play with the reflections from the different layers.

Also, also: CD’s make awesome diffraction gratings, for pretty much everything.

Also, also, wik: set up a cube of mirrors with the mirrored surfaces facing in. Drill two holes in the box and shoot a laser in one of the holes such that it comes out the other hole. Now mess with the angle of the box to the laser to create a bunch of bounces that still comes out the other hole. Take one of the mirrors off and clap some Gold Bond in there. Fun for hours.

Radiation:

Other than fighting the typical misconceptions (that radiation is some sort of fluid that gets leaked from nasty things–like bombs–and contaminates the environment like oil or Ke$ha) radiation is fun to teach because everything interesting uses it somehow.

Here’s how I’m going to start things off:

Thnx osxdaily

Kids love this kind of stuff; debunk someone’s fantastic claim. Ok! Does putting your phone in a glass help reception? How about foil? How about plastic? Let the inquiry begin!

Oh, how to measure? Here’s how:

iPhone:

  1. Call *3001#12345#*
  2. Hold the bezel button until the power off slider appears, don’t slide it
  3. Hold the home button

Android users can access the same information from their settings menus (about phone, maybe?) This is a measurement in decibels, which is another awesome conversation. Don’t tell them anything, let them get intuition for it. Also, -50 is the best I’ve ever seen.

The refresh rate isn’t that fast, but it’s a cheap way to measure signal attenuation. It might even be fun to map out the local area. Maybe perhaps during electrical weather?

From here it’s not too hard to see direct instruction involving Gauss, surface integrals, radiation types, and all that.

Thermodynamics and Code:

Thermodynamics is by far the most cryptic and powerful descriptive of the branches of physics. The professors of thermo always seemed a bit Hogwarts. This is cute in college, but the business of secondary school is not to wow students with mysticism, it’s to inspire them to pursue study in things that they didn’t even know existed months prior.

To do this, I think you have to settle on the concept of entropy. It’s the most wily and important law of thermo, and the most ill invoked later on, and the most enabling physics concept for non-physicists. I have a hunch that encryption and security is the best lens for entropy.

Here are some fantastic videos from Jason Briggs (@gotphysics) about RSA encryption. That said, a fun discussion about hashing, salting, and encrypting may be good at this point. (that is, hashing is irreversible, encryption is, and salting makes everything orders of magnitude harder to hack)

I suppose the initial investigation will be about brute force hacking. Something like this for the kids to play with in Processing:

Screen Shot 2012-12-24 at 11.25.18 AM

A terrible brute-force hacker, from me to you.

I like programming because it raises the degrees of freedom conversation early on.

Also, here‘s a great WIRED article about the end of the password era. Perhaps kids could be set to coming up with behavioral solutions?

Fields and Charges:

Balloons.

That is all.

Ok. That’s not really all, but seriously, rubbing balloons on heads (especially in winter) is probably the most awesome way to motivate lots of electrical ideas.

Here’s how it plays out. I make a fool of myself and hair, and I make the subtle leap from hair to physics by asking what the free-body diagram on a single hair is. This leads to a lot of questions about what magical forces are keeping things up.

We end up with lots of investigations about charging the balloons. I have the students make whiteboards about what they discover simply by playing with several balloons.

Most kids attempt to float a balloon with a base of other charged balloons, I’m not sure why, but this happens every time. Other students will put things in between two charged balloons to see if they can affect the repulsion or attraction. As you can imagine, the play phase of this investigation is really generative.

As a teacher, this lesson is a pedagogical mine field. I have to make sure that I’m paying attention to the little things they say, things like, “Rub it four times on each of your heads, then float it.” These things can lead to other, more science-y investigations, like building an electroscope (with foil, paperclips, and a clear Dixie cup)

Let this discussion get philosophical. They need to be able to admit that we NEED another force here, and electrical force. If you don’t motivate that here, circuits will stay magic to them for a long long time.

What’s more important, is that, of all things, the behavior of balloons necessitates adding a force model to physics. There’s no good explanation for the ability of a balloon to levitate another balloon one moment, and then the next moment, after being grounded, they do nothing. So, how many other forces are we just going to make up?

This is clutch and leads to an oft requested lecture on particle physics and the standard model. That is, every force is really a field of particles being exchanged like bowling balls between to people on ice skates. Whether or not fields actually exist is immaterial, the math works, it got us to the moon, and it describes how your computer thinks. How’s that for some philosophy of science to stick in the ol’ craw?

Some necessary problem solving happens here. How does gravity compare to this new force? What particles feel what forces? We always work out the is-gravity-the-attracting-nucleon-force problem, a classic at the dinner table. Of course gravity isn’t, another force (strong)!

Oh, and the people at the now largely decomissioned Fermi National Laboratory are awesome at field trips.

And all from balloons.

Magnetic Flux, Potentials, Fields, and “Mass”:

I find magnets really hard to teach. The big idea is potential energy, but for some reason I can’t find a good resource to get that across. In a sense, we’re all just really far out of the magnetic well of most magnets, so bringing them together really only frees up energy that was already stored in the flux of that field. That’s hard to buy, because you have to see the world as a billion magnetic fields all mushed together mathematically.

What’s even harder to deal with are the things we all learned in middle school. It’s not that the opposites attract trope is wrong, it’s just that it doesn’t motivate anything. There’s a mystery here, and I think that’s way more fun to think about than the force from an infinitely long current carrying wire has.

Like, for instance, wtf do magnets not attract charged objects? That’s a good 2 days of class proving that.

Here‘s a great example of the kind of crap I’m talking about. Sure, they do a great job of repeating the same distilled results of some really classic experiments, but it doesn’t cause kids to ask the big questions, which, in the dipshitery of the Insane Clown Posse, “@#%#ing Magnets? How do they work?” (Thanks, Greg, for the edit)

Here are the big ideas:

  1. Some things have magnetic fields because they are ORGANIZED, which takes energy to do (entropy).
  2. Some things can be magnetized, and predicting what those things will be is fun and challenging to do.
  3. Magnetic field lines join together like weird squid arms, which somehow predicts the forces that will be present.
  4. No, magnets do not produce energy, the energy was already there (see above). Some of you will want to say something like, “Magnets can do no work.” Kids don’t understand that, so take your college education and put a semi-colon in it.

Want a hard and fast rule about teaching? In high school, we must do things. We must move. We must build. In college, we admit to liking something as more than friends, and we then study it of our own obsessive volition.

COILGUNSARETHEBEST: So, go to Walmart, or Target, or wherever, and ask for every already-developed disposable camera body they have. Take the giant bag the give you, and let the kids crack them open.

Then, show them this, or not:

Basically, just replaced the flashbulb in the camera circuit with a coil of wire and a nail.

From the camera circuit, much can be gleaned and many direct instructions instructed. Such as, how transformers work, transferring from DC to AC and back, storing energy in E fields, etc…

My favorite camera related lesson is using energy conservation to go all the way back to the change in the battery’s voltage by measuring the height of the nail when it’s shot from the coil. Love it.

ALSO! MAGNETILES MAKE A CLAIM. PHYSICS WEIGHTS IN:

magnetiles physics

How is that possible? Seriously? I think I have it figured out, but just think about the things students will have to grapple with to explain such an awesome toy. Aside, If you have smaller kids, I would suggest buying the 100-piece, translucent kit and some glow sticks.

Circuits:

I would recommend this Arduino kit for labs.

Why teach circuits with Arduino instead of the typical Ohm’s law, Capacitors, Inductors, AC sequence? I don’t know, maybe because that stuff is the stuff of antiquity? Maybe because high school isn’t about creating perfectly prepared physicists and engineers? Maybe because I want them to be pumped about electronics instead of bored by making equivalent resistors from Mr. Electronics fancy resistor puzzles!

Download Arduino (it interfaces with Processing nicely, btw, ftw, bbq). I’m currently building a power glove with flex resistors so that I can control a game programmed in Processing where each finger controls a different thruster on a spaceship.

Yeah, Arduino is the best. Here are some project ideas.

Need help learning about it? Go talk to @achmorrison, he taught me.

Llama: Fermi problem! How much energy is wasted by leaving DC converters plugged in while not using the devices they power? You can take data with an IR thermometer!

Also wik, this article on compressed air “batteries” is awesome. Think about the things the kids will ask?

Finally, go through every common household circuit and make them build it. Two switches for one light? Ok! A rheostat dimmer? Ok! Magnetic ballast? Yay! Breakers v. Fuses? My favorite!

I even go so far as to have them wire up doll houses that I get at consignment stores. You can get wire and switches at your dump/landfill/freecycling center (if you live in Seattle), if your center knows what it’s doing, it’ll have an electronics reclamation center.

What’s it all mean, Basil?

It means that I just wrote down all of the things I don’t want to forget to do next semester.

Remember, your goal is to build hooks for things to be hung on later. Don’t let the idiots at your state capital tell you that a temporally proximal test score in any way correlates with the time span on which education actually works (decades), just keep building hooks and talking about content when you have to.

Love, Shawn.

 

Shawn Cornally • December 29, 2012


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