Lerner Physics

So, it's Wednesday, and due to our schedule, I don't teach AP Physics 1 today. So, instead of a teach180 entry, I've decided I'll use this time to write about something I can't fit into a typical #teach180 post.

Here's a post I started in November, and never posted. I think it's worth posting, and I have some questions at the end:

At a professional development meeting last week, Dr. Lori Wilfong spoke about how to teach vocabulary effectively. As an AP Physics teacher, I didn't know if it would be helpful, but I played along. I went through a few exams, looking for the words that I thought would be most powerful for an AP Physics student. Dr. Wilfong separated vocabulary into three tiers, and I used those tiers to guide my thinking. I didn't include any tier one words, which only have one meaning and that they'll probably know before entering the class. And I only included the most important tier three words, those words that are the specialized vocabulary of the subject matter. I looked for mostly tier two words, words that take on different meanings depending on how they're being used. I think the list is very powerful, and I think that students who consciously tried to know and use these words correctly would be at a great advantage. 

Here's my list:

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I teach two sections of AP Physics 1. They're both in the morning. They both have the exact same number of kids. They both had the exact same amount of time to do a lab with motion detectors. As two classes, though, the vibe couldn't be different.

One period talked about all the different situations with the motion detector pretty quickly. All the students basically agreed, and the questions seemed mostly limited to questions about the conventions of the representations. (Do the axes have arrows on them? When do the arrows go on the dots in the motion map?) When I was done, I was uneasy that they had not yet made their intuitions explicit. So we made a class consensus focused around two questions: how we show the direction of motion and how we show if the object is moving fast or slow in these different representations.

The other period, when going over the different situations, got into it. Some students seemed to want to represent what they actually saw in lab, while others were more willing to idealize it (use their "physics goggles"). Students could reason between the representations and give arguments for their answers. Not all of them, though, saw the situation the same way. It got a little hot. All the answers they whiteboarded were reasoned and not intuited. Even if their reasoning was not the same reasoning I would use, it was consistent and intelligent. By the time we did the class consensus, which I felt I should do, partially because I did it in the previous class and partially because I wanted to make sure we all ended up in the same place, every student was articulate about how to answer the two questions. The arguments were productive, but a bit too critical.

When we moved on to the next activity with the second class, I knew it was time to pull out Kelly O'Shea's Fun-Time Super-Cool Mistake Game™. (That's not what she calls it, but that what I call it in my head.) The mistake game is great; I learn more every time I read Kelly's post. I'm introducing it here because students were passionate about their answers, which is good, but were phrasing everything in terms of "right" and "wrong." I contributed to that; they started to echo my language about what I like and don't like by exclusively talked about what they don't like, meaning what they thought the whiteboard got wrong. This is a trap I fall in all the time, and Kelly O'Shea's Fun-Time Super-Cool Mistake Game helps me get out of that trap. I need to shift the conversation to questions like "According to the motion map, where does your object start? How does your motion map show that?"

After just quickly introducing the four ways to represent constant velocity motion of a particle (see my last post), I sent the students out to try to walk various position-time graphs, and then use the computer to find the velocity-time graph, and then represent that motion as a motion map and as words.

Some questions my students were thinking about today:

• Is going towards the detector the positive direction or is going away from the detector the positive direction? (Student tries it.) Wait, really? Why is going away positive?
• Do I ignore that first bit where I'm not moving yet, or do I draw it on my velocity-time graph? 
• Can I just call where I start x = 0? (As in, if I start where I normally start a little ways away from the detector and don't move, can't I call that point zero?)
• How does the velocity change in an instant? Doesn't it take time?
• How can I tell which way to draw the arrows on my motion map?
• How does the slope of the position-time graph relate to the velocity of the object? (One student came up with a great rule for this. I don't want to put his or her name in here because I didn't ask for permission, but every time I came back to that group, I always went back to that rule, naming it after the student who came up with it.)

What does summer work look like for AP Physics 1? I don't want them to start doing any physics, because they don't know how the class works yet. But summer work is a good way, I think, to have students check in with their math skills and see if they know some of the mathematical moves they'll use in the class. I've posted two pages from the seven pages of the summer work above. The other pages are about simple trigonometry and literal equations.

We whiteboarded this problems today. I was happy to see that classes were ready to ask each other questions, without putting all the questions through me. 

After that, it was time to sketch out, quickly, CVPM (the Constant Velocity Particle Model). Many units in this class are about the four representations we use to describe them:

• Diagrams: I introduce the motion map by doing an example. Sometimes I'll talk about a car with a leaky fluid. Other times, I refer back to what students did in lab to measure the speed of the buggy. I don't spend too much time on it. I focus on doing one quick motion map, asking if students can tell where are walked faster/slower/stopped, when I was walking forward/backwards, and move on.
• Algebra: Another quick one. At this point, I don't want to show all the equations we could use. Some students, as soon as they see an equation, use that representation above all others. I understand why; they take years of classes in the math wing where the equation is the best representation. So I try to deemphasize it as much as possible. I ask students what equation they used in math class to solve questions about speed. Here, I usually hear s = d/t; at other schools, I've heard D = RT. I write down either. I ignore it for now. (Later, when we've developed a good equation for velocity, I'll add it to the notes here, but not yet. I'm just keeping this representation open as a possibility.)
• Words: What words will we use for to describe this motion. Starting point, velocity, fast/slow usually come up quickly. I often have to give an example until forward/backward comes out. I don't like forward/backward because in this model, points don't have a front. I will sometimes do an example where I walk both forwards and backwards from the left side to the right side of the room. My belly button does the same motion, even though one is forward and one is backward. So I tell them, since I'm mathematical, I prefer positive direction/negative direction.
• Graphs: We found from doing the buggy lab that graphs are a great way to show your results. So a straight line on the position-time graph means constant velocity. We then answer these two questions: What does the vertical intercept mean in this graph? What does the slope mean in this graph? They are very useful, and that fact allows me to reiterate how important graphs are to physicists.

I don't always teach these four representations in this order, but I wrote them in this order because it's how I remember to do all four. I use the acronym DAWG. It's very 1990s, but it works for me.

Students whiteboarded their results for the buggy lab, and it was a lot of small handwriting, long tables, and half-hearted conclusions. No one, in words of Brian Carpenter, was willing to bet me a burrito on their results. We did come up with a list of things we wanted to see in whiteboards in the future: large, legible handwriting, multiple trials, and visuals would be nice. On the way home last night, I was thinking what would happen if we lined up all the whiteboards together. That's where the picture came from today, with many students timing the buggy for 9 meters every meter. I didn't like how teacher-directed it was, but my students and I did like how convincing the results were:

So, last year I blogged my combined AP Physics 1 and 2 class. This year, I'm going to do a #teach180 blog for a AP Physics 1 class. I have a student teacher this year, so I don't know how many days of the teach180 I'll get done this year, but I do want to blog a bit this year.

Today was the first day, and I wanted to get right to the lab. So we started the buggy lab. If you don't know about the buggy lab, Kelly O'Shea has an amazing description. We listed our observations; we figured out we would measure time. I do a lot of this lesson like she does. Thanks, Kelly (as well as Brian Carpenter and Chas Deremer.) 

But then, when they wanted to use metersticks, I told them I couldn't find them. All I could find was a long measuring tape. So we could only measure the position of the car on the measuring tape rather than the distance from the start line. I like this move. We start with position this way. I also don't quite set my students up to get position-time graphs on the first lab. I like to see what they get without much guidance. (Also a Brian & Chas move.) When they all whiteboard their information, and see what a graph can do, the class often agrees that graphs are the best way to see all the information quickly. I like the discussion that comes out of this confusion.

I also learned something about the question "Is the buggy moving at a constant speed?" Some student hear that as "Does the buggy do the same thing every time?" rather than "During one time down the track, does it stay at the same speed during that one trial?" I'm not sure how to avoid that confusion. 

We finished the curriculum! We have more practice to do, and tests, and other such stuff, but the end is in the sight.

We ended with a whimper, not a bang, by talking about neutrinos and half-lives and picking up those last little bits of what's left in modern physics. 

As I look back at the first few blog posts, I notice I used to write a lot more each day. I was at the beginning of the marathon we call a school year and not at the end. I also don't want to give away too much. Not too other teachers, or my students this year, of course, but to future readers of this blog, future students who might look here and know everything. It's a silly reason; I see lots of great physics bloggers talk about their every move in class in detail, with answers. But I shy away from telling too much.

Writing this blog has been worthwhile to me. I'm trying to think about what I'll do next year to keep reflecting on and improving my teaching.

We whiteboarded our last photon model of light questions, and the best part of today was the questions. That seems to be my new theme; their questions are so well-crafted and incisive that they should be celebrated. What are the different ways we can define intensity? Why can't an electron just absorb some of the energy of a photon?

And then we moved to special relativity, and the questions kept coming: How is this related to time travel? How much energy would it take to accelerate me to close to the speed of light? What does it mean that "that astronaut" traveled 0.5 seconds into the future?

Now they want to study a lot more special relativity.

It's more of me talking, and my students asking lots of questions. They love it. I don't really know another way.

The goal was to talk about the different conservation laws for nuclear reactions: number of nucleons, charge, mass-energy.

But it opened up so many other questions, including anti-matter, black holes, and dark matter. I tried my best to answer. The conversations were rich and interesting and the questions were great, but I was the sage on the stage. 

I can't wait until they start reading about all these topics and start teaching me. I'll have to wait to the book project after the AP Exam.

We played around with various different gaseous atomic spectra. They are so interesting! Neon looks so red, and the sample marked "air" has so many different lines. We took some artful photos through our cameras, as shown above.

We didn't get quantitative with our observations; I wasn't sure if it was even going to work, but I think next year we can get quantitative. The lines are bright and easy to see, even through cheap diffraction gratings.

We are definitely finishing the year, and, just like last year, when we get to the end of the year, the questions about quantum mechanics are good. Quantum mechanics is weird. I try to explain, and I also try to postpone. I'm not a quantum mechanic!