Bouncy Ball Graphs

One of my favorite tasks for students to do is to create well-coordinated position, velocity, and acceleration vs time graphs for a bouncy ball, where careful attention is given to the moments of contact with the floor. I got this task from my high school physics teacher, but it’s in Arons’ book as well. The future physics teachers have this as a content standard in my class. There are many predictable obstacles, but the real meat I want them to get to is reasoning about the acceleration. This is so not easy for them-partially because they mostly know acceleration through special cases, and partially because they aren’t strong in thinking about vector kinematics. Mostly students say the acceleration is constant. It’s like the bounce isn’t even on their radar when considering acceleration. Part of what I like about it, is that students know enough to get started and the task itself is clear. My job when they ask to assess, is to keep them talking until they notice some inconsistency, and then to help them orient to that inconsistency and how they knew there was something wrong. Then I send them off.

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Help! We need to do better.

One of our recent physics teaching graduates took a mid-year vacancy teaching 8th grade physical science in an struggling urban area. There are many factors making this job particularly difficult for the student, operating under survival mode.

  • The new teacher is coming into the classroom mid-year, with students who have had a substitute for the past month
  • Between the interview and first day, there were four days, little to time to prepare and get oriented.
  • The school appears to have no induction process for new teachers
  • The school really is a struggling / failing school, both by qualitative sense and quantitative measures
  • The population this teachert is working with is very different than populations he experienced while student teaching
  • Our existing program does too little to prepare students for classroom management
  • Both the students’ content and pedagogical knowledge better prepared him for teach high school physics than middle school
  • Our program doesn’t yet properly support students in making job decisions and initial/ongoing  support.
  • Our program doesn’t yet have students leaving us with any fail-safes like, if all else fails, “Here is exactly what you are going to do the first month you are teaching, and here is a basket of all the things you’ll need to pull that off.”

By far the biggest problems he is facing is typical for new teachers–classroom management. One of the things I’m wondering is, what role can the physics department play in preparing / supporting students in this way? I mean, I can say, well, “Shouldn’t the education classes deal with that?” But I think that’s just punting on responsibilities to put our physics teacher in the best possible position to succeed.

I feel like that last bullet might be the thing that we can change the most in our department. Make sure that when students leave, they have very specific plans in place, including activities oriented toward setting classroom expectations. A kind of thing that can carry them through that terribly difficult beginning. And the second thing is for us to be more involved with them in the decisions they make for jobs.  And obviously, we need to better coordinate with education side on initial and ongoing support, because we can’t do that alone. But we should be involved.

Help! What do we need to do? What do we need to think about? Grace, I’m looking at you especially.

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Vulnerability

The first two days of the teaching of physics were a bit unnerving for me and for students this semester. Students ended up being confronted with a lot of things they didn’t know, or weren’t able to do, or didn’t understand–mostly things they were confident they knew, were able to do, and understood. The feeling in class was tense-confidences shaken, identities threatened, feelings of shame rising…

But, today, for whatever reason, we emerged more gracious, more accepting, more willing to be wrong, more willing to open up, more willing to sit with confusion, to listen to others’ confusion, more willing to lean into to the unknown and face it admirably.

More than anything, that constitutes significant progress.

I am asking a lot of these students this semester–a lot of reading, a lot of synthesizing,  a lot demonstrating mastery of physics concepts, a lot of practice teaching, a lot of learning about student thinking, a lot of applying what they’ve learned to new contexts. I am likely going to overwork them to more than one breaking point.

But the hardest thing. The hardest thing may be the vulnerabilities I am asking them to step into and embrace. At least for today, we stood together, courageously so.

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Readings I’m using in Various Science Teaching and Learning Courses

This semester, I am teaching (i) an inquiry course for future elementary school teachers, (ii) a teaching physics course for future physics teachers, and (iii) a teaching and learning seminar for physics majors who are serving as undergraduate TAs in one of our reform-oriented introductory physics courses.

As semester goes on, I’m going to try to keep up updated reading list for each of the courses. Here’s where we are thus far…

Inquiry Readings:

Week 1:

“The Pendulum Question” from Seeing Science in Children’s Thinking: Case Studies of Student Inquiry in Physical Science by David Hammer and Emily van Zee. [Video portion discussed in class on first day]

Week 2:

“The virtues of not knowing” from The Having of Wonderful Ideas: And Other Essays on Teaching and Learning by Eleanor Duckworth.

Teaching of Physics Readings:

Week 1:

“The sun goes around the earth–Goals of Science Education” from An Inquiry into Science Education: Where the Rubber Meets the Road by Richard Steinberg

“Student Inquiry in a Physics Class Discussion”, in Cognition & Instruction, by David Hamme

Week 2:

Selected sections of “Chapter 2: Rectilinear Kinematics” from Teaching Introductory Physics, by Arnold Arons, paired* with “Building the Constant Velocity Model” over at Physics! Blog! by Kelly O’Shea.

Every student will read one of the following papers and with a group give a brief presentation of the research, its findings, and discuss how a PBI problem they did earlier seems informed by this research.

Teaching and Learning Seminar:

Week 1:

“Unpacking the nature of discourse in mathematics classrooms” in Mathematics Teaching in the Middle School, by Knuth & Peresseni

Week 2:

“Questioning and Discussion” from Teaching Secondary School Science: Strategies for Developing Scientific Literacy, by Bybee, Powell, and Trowbridge.

Week 3:

“Reflective Discourse: developing shared understanding in a physics classroom” by Van Zee and Minstrell. (1997)

———-

* An explicit goal of mine in teaching of physics to pair readings–one that is closer to the trenches of teaching and one that is closer to research. Both of these reading are fairly close to teaching, but Kelly’s writing is like your are in her classroom, and Arons writing is a bit more distant.

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Revoicing and Retrospective Recontexualisation

Lemke writes in “Analyzing Verbal Data” about the concept of retrospective recontextualisation

“Discourse forms do not, in and of themselves, “have” meanings; rather they have a range of potential meanings. Words, phrases, sentences are tools that we deploy in complex contexts to make more specific meanings, to narrow the potential range of possible meanings down to those reasonably or typically consistent with the rest of the context. Even in context, at a moment, an utterance or phrase may not have a completely definite meaning. It may still express a range of possible meanings, differently interpretable by different participants or readers. This is very often the case at the point where it occurs. The context needed to specify its meaning very often at least partly follows its occurrence. So it may seem to have a more definite meaning retrospectively than it has instantaneously. In fact, depending on what follows, its meaning, as participants react to it, can be changed radically by what follows (retrospective recontextualisation).”

I thought about Lemke recently while reading Alex Barr’s post* about productive prior knowledge. In that post, he describes a discussion he had concerning the common misconception about the moon’s phases (i.e., the earth’s shadow is cast on the moon), and how you can think about that misconception in terms of kernels of productive knowledge (e.g., the moon itself blocks light from getting to the back half).

Lemke argues in the above passage that the meaning given to any student utterance happens in interaction, in part based on what proceeds the utterance itself. I’m imagining this in the context of teacher re-voicing. Specifically, I was imagining three different revoicings that might occur after a student makes a statement like, “The phases are casued by the earth’s shadow falling over the moon,” and how they might, retrospectively, change the meaning of the student utterance. Here’s the gist of several possible re-voicing.

“It sounds like you are trying to draw our attention to an important idea we should consider in explaining the moon’s phases–light from the sun can be blocked by objects that get in the way. “

“It sounds like you are saying that there must be something blocking sunlight from getting to certain parts of moon. And you’re proposing that one thing that could be doing that blocking is the earth.”

“So your idea is that if the earth were to block some of the light from getting to the moon, then we’d see changes to how much of the moon is lit.”

“It sounds like you are saying the

Its interesting to me how these different voicings may (or may not) change the meaning of the student idea. The first one (in my mind) attempts to re-voice the idea by focusing on what the teachers know to be a kernel of truth, downplaying subtly what is not true. The second one attempts to re-voice the idea as a particular case of a more general principle, perhaps opening up the idea, giving it room to breath and be connected to other ideas. The third one re-voices the idea as a conditional proposition–one that the teacher knows to be true about lunar eclipses. A more straight forward re-voicing such as, “It sounds like you are saying that the phases of the moon happen when the earth blocks light from getting to the moon,” seems to narrowly frame the idea, sort of pinning it down, giving it no where to go. The re-voicing doesn’t help to put the idea in a broader context or to highlight any parts of it as being more or less significant.

One reason I’ve been thinking about this so much is because next semester, one of the goals for teaching of physics is to develop skills at facilitating classroom discussion. One of the discourse “practices” we will focus on is “re-voice and toss“. There are of course, lots of reasons for re-voicing, but I feel like I’m circling around something here… hopefully more to write on this later.

* Alex is a burgeoning physics education researcher at the University of Texas at Austin, who you should say hello to, get to know, and keep your eye on. *

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Teaching Evaluations Data

I’ve been making my course evaluations public since I got here. Here they are again, whatever they mean.

Physics Fa 11 Sp 12 Fall 12 Dept Avg
Presentation 4.9 4.9 5.0 4.1
Organization 4.8 4.8 4.9 4.0
Assignments 4.8 4.9 4.9 4.3
Scholarly 4.7 4.8 4.9 4.0
Interactions 4.9 4.9 4.9 3.8
Motivating 4.7 4.7 4.8 4.0
Overall 4.5 4.6 4.5 3.7
Inquiry Fa 11 Sp 12 Fall 12 Dept Avg
Presentation 4.4 4.7 4.8 4.1
Organization 3.9 4.3 4.4 4
Assignments 3.9 4.3 4.4 4.3
Scholarly 4.0 4.2 4.7 4
Interactions 4.5 4.6 4.9 3.8
Motivating 4.2 4.6 4.6 4.0
Overall 3.0 3.5 4.0 3.7

 

 

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Notes to Self about Engagement with the Seasons

For the seasons unit, I’ve done a fair amount of giving students data sets to graph, looking for patterns, similarities, difference. We have been doing so in order to build evidence for or against various claims about what could cause the seasons. I think we’ve learned a lot along the way.

Anyway, there are two observations that have driven student a fair amount of engagement, and I don’t want to forget them:

#1 McCurdo Station in Antarctica has the sun shining on it for 4 straight months, but its average temperature is still below freezing during that time. [If duration was only factor, then we’d expect McCrudo Station to be very hot]

#2 In June, Murfreesboro, TN is 20 degrees hotter than Quito, Ecuador. [Shouldn’t the equator always be hotter?]

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Beginning a Short Unit on the Seasons

So, we are ending the year in inquiry by studying the seasons. We started by talking about the following situations:

(1) You are at a concert. What could you do to increase or reduce the impact of the sound on your ears?

(2) You are by a fire. What could you do to get hotter or colder?

After they muddled with those situations, I introduced a third test case.

(3) A person in the room has a smelly perfume? What could you that would make your experience of the smell more or less intense?

 The goal was to generalize a set of general patterns on what affects the intensity of “emanating stuff”. Our initial list was the following:

Volume (how strong the actual source of smell, sound, or heat is)

Proximity (how near are far you are from the source of smell, sound, or heat)

Duration (how much time you spend around the smell, sound, or heat)

Protection (how many barriers, blockers, or filters are between you and the source of heat, sound, smell)

We went into the detail explaining how these might work in each case, but that’s the gist.

An Experiment to Foster Thinking about A New Mechanism

Two identical heat lamps were set 10 inches away from a sheet of paper. Under the sheet of paper was a thermometer. The identical lamps fixed the volume. The 10 inches set the proximity. We set the duration time to 1 minute. The identical paper fixed the level of protection.  One lamp was set to shined directly down on the paper, and the other was set to shine at a very shallow angle (being careful to keep the 10 inch separation from the thermometer).

Students were asked to discuss what would happen to the temperature when I turned on the lamps.

Most groups believed correctly that the lamp shining straight down would make it hotter. Here is how we eventually built pieces of an explanation for why angle matters:

  • You are more likely to be burned by the sun from in the middle of the day, than the morning or evening, the sun’s rays must in some way be stronger when overhead than we angled low in the sky.
  • Direction also matters for our previous example. With fire, you can turn your cheeks toward fire to give it more direct access to fire’s heat. With a sound you can turn your ears away. With sound, you can turn your nose away.
  • With angled light, the rays of light hit the paper at a shallow angled creating a “glancing blow“, like skipping a stone on water, or a car hitting a wall at angle (vs. throwing a pebble straight into the water or driving you car head-on into a wall). The shallow angle creates only a glancing blow, which has less impact than a “head-on” collision.
  • With angled lamp, the light rays end up hitting a large area on the paper; where as the angled down rays hit the paper in a small area. This changes the concentration of the heat. It’s like heating up a large room or a small room with the same space heater. The large room will take longer to warm up, and may not even get up to same heat, because the heat gets spread out more.

We did the experiment, and in one minute the overhead lamp heated the thermometer to 130 degrees, while the angled lamp only heated up the thermometer to 78 degrees. Huge difference. I even rigged the deck in opposite way so that the angled lamp was actually closer than 10 inches and it got the thermometer that read a little higher. It was no contest. We added a new factor to our list, so that we now have:  Volume, proximity, duration, protection, and now direction.

Our goal over the next 3 days will be to figure out which of our 5 factors are most significant for explaining the seasonal changes to temperature–that is to collect evidence and arguments for the relative importance of each and to refine our sense of mechanism about how they work in the case of earth.

Why I’m liking this approach?

#1 We are drawing on knowledge from everyday experience : sitting by a fire to keep warm, smelling something rotten, being around loud music, etc. Had I asked what causes the seasons, it would have been about orbits and tilts. That would lead us down a frustrated track of sterile and unproductive school knowledge.

#2 We were generalizing quickly from a set of particulars, and naming them to help support generalization. We were not not just swimming in a vast sea of specific situations, and hoping that abstraction and connections were made. I specifically asked them to connect case specific mechanisms and to come up with general names.

#3 We are making sense of contrived situations in terms of everyday mechanism, such as getting burned, car crashes, skipping stones, and heating rooms. While I suggested the situations early on, students quickly extended to and built on other everyday sources of knowledge. This suggests that I helped “frame” the conversation as building on everyday knowledge. Going to the contrived could have tipped us out of, but it didn’t.

#4 Keeping the initial conversation away from the learning target (i.e., the seasons) and toward other phenomena (i.e., fire, sound, smell), keeps my “misconceptions” ears from perking up. Instead, I’m listening for useful ideas, analogies, observations, mechanism, insights, etc.  My listening patterns in turn influence my interactions with students, which in turn influences the nature of the discourse that emerges. My commitment and ability to focus on the good students say rather than the wrong stuff depends on the context I set up. I’m setting up a context, not only in which students will hopefully draw on everyday ideas productively, but I’m setting up a context in which I will be more likely to hear and draw on their ideas productively.

#5 I hope this will get us to “tilt” last, which is the empty vacuous understanding that many students have. Instead, I hope we will initially focus our explanations on locally observable changes, such as changing amounts of daylight and changing altitude of the sun in the sky. Tilt will be, hopefully, for the purpose of explaining the changing daylight and changing altitude. Thus, changing daylight and changing altitude will be the explanation for the seasonal variation in temperature.

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Big Questions for My Teaching of Physics Course

In spring, I’m teaching “Teaching of Physics” again.  Here is my stab at trying to organize my thinking about that course around 3 big questions:

Understanding Physics: What does it mean to understand physics content in deep and meaningful ways? What do such understandings look like in general? What does this look like in particular with respect to the specific domains of physics content that I will likely teach?

Learning Physics: How does meaningful physics learning develop? What do my students need to be engaged in for this to happen? In what ways are exemplary physics curricula / instructional practices organized to engage students in these ways?

Teaching Physics: What do I as a teachers need to know and to be able to do to effectively orchestrate exemplary instruction that supports students in meaningful learning? What practices and habits of mind should I consider high-leverage and generative for me in developing as a teacher?

I’ve tried lots of other ways of organizing it, but this is where I’m at now.

Next steps:  

(i) What specific learning outcomes do I think are most important?

(ii) What would count as evidence that students have learned those things?

….

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When a Student Teaches the Teacher about Teaching

Today, I didn’t have time to revise the sample problem I’m supposed to do in physics. So I worked the sample problem as given. We were doing standing waves. In the particular problem, there was a string with both ends fixed and we were told it was vibrating in the second harmonic. In this case, the wavelength is equal to the length of the string.

After my sample problem, students were given a problem where the string was vibrating in its fifth harmonic. A fourth of the class did it correctly, drawing it out and concluding that the wavelength must be 2/5 the string length. Half the class did it wrong saying that the wavelength was equal to the string length. And a third of the class said the wavelength was 5/2 of the string length. As I was walking around, I asked a student why they thought so many people were making these mistakes.

She responded without hesitation, “The sample problem was poorly designed. You shouldn’t have given us an example in which the wavelength and the string length were equal. That makes it easy for everyone to think that’s what you are supposed to do every time. Plus dividing by 1 or multiplying 1 gives you the same result, so it’s easy for people to mix it up. Next year, you should use a different harmonic to set up the problem.”

I wish my future physics teachers knew had to unpack a sample problem like that, and see how it might lead to over-generalizations and misinterpretations.

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