A Shift!

Something really awesome happened today, that I unfortunately didn’t adequately document with pictures!! So this will have to do… I’ll explain in a moment.

We started our energy unit with an “Energy Stations” class, during which I was mostly hoping to establish common experiences for the future and pique curiosity about these phenomena. We played with wind up toys and poppers and pendulums and genecons crank-generators, and students thought about “How does this station illustrate energy storage? How does it illustrate energy transfer?”

Problem was, students had no common language or understanding with which to even begin to answer those questions!! So they definitely had a chance to be curious and play, but it wasn’t really connected to energy in any concrete way. I knew this beforehand, but I didn’t try to avoid it.

After the lesson, another ninth grade physics teacher came in, and we regrouped about how it went… We talked about the NEXT day’s lesson, which was an introduction to bar charts and energy transfer using the PhET Skate Park. At some point late in the conversation he realized that the order of these two lessons was totally reversed – that an introduction to the three energy forms in the Skate Park would totally change the energy station experience. They’d have some understanding to call on related to those specific forms, and they’d recognize the need for other forms to explain all these other processes! We quickly made copies of the Skate Park handout for his class that started in 10 minutes, and I modified my afternoon class accordingly.

Two things about this: First, this would never have happened if I was the only physics teacher in the school. Those conversations are essential for hashing things out.

Second, I’ve been trying to diligently complete these Self Evaluations for my class with Eugenia at Rutgers, and this was PARTICULARLY fascinating. My “Before” reflection was full of doubt, and I didn’t have any good answers to the important questions in the reflection (like, “How will you know students are learning?”). I should have caught the flaws in the lesson before it went live, but catching them immediately afterward was almost as good. So I’ve completed 2 each of the “Before” and “After” reflections today, and the contrast seems profound!

If anyone’s curious to see the reflection, it’s partly based on the “RTOP”, and another rubric that was developed at Rutgers. I put it online for convenience, but that also makes it really easy to share!!

##setbacks ##etm ##reflection ##phet

Pasta Bridge Prediction

Today we’re finally done with round one of our experiments, measurements, and analysis unit. The climactic practicum involved predicting a range of values for the number of marbles that will break a pasta bridge. A correct prediction with a range of 20 earns 1 HW point, and range of 10 earns 2, and a range of 5 earns 1.

Because the phenomenon itself is so variable, a wide range is wise. This group settled on 110 to 120 marbles, and the result of our test was 118. Hurray for best fit lines!!

##expdesign ##physicsfirst ##uncertainty ##practicumlab

College Physics

Today was exciting because my demo copy of Eugenia Etkina’s new “College Physics” text finally arrived!

I flipped to a page in the forces unit and there was a QR code for a video showing that friction depends on the normal force. No narration, of course… Just physics. Awesome!!

Speaking of AP, my class found the velocity of a water balloon shot out of this launcher. On Tuesday, they’ll be trying to hit me with one of these very same balloons from some set height and distance with one of these same balloons… The things we do for physics learning!!

##ap ##isle ##pmm

Predicting a Range, and AP Accelerated Motion Challenges

Students took a quiz today, on making graphs and identifying the independent and dependent variables in an investigation. After the quiz, we played “data table Jeopardy”, where students looked at a graph of a pasta bridge experiment that I’d done, and tried to construct the data table that was used to make the graph. (This was the idea of another ninth grade teacher, and it was a perfect challenge!!) The graph had a lot of points for each bridge thickness value, so we started talking about variability, and what a range of values would refer to. I try to get students to think carefully about uncertainty in this way – what range of values would make sense, given the measurements we’ve made. This the. Set the stage for the test of the prediction next class, when we’ll try a previously unmeasured bridge thickness!!

In AP, we’re talking about multiple representations in the context of acceleration. Students have all had physics in ninth grade, so we’re really able to bit the ground running and spend time doing some cool stuff. Using kinematics concepts AND Newton’s 2nd Law, students tackled three different challenges in six groups. These challenges were:

Predict the distance traveled by a steel ball shot off a push-pull spring scale!! (Tricky, because force is actually a red herring here…)

Predict the minimum time and distance it would take to accelerate a cart to 1m/s using a piece of spaghetti.

Determine the mass of a bowling ball using a ruler (to push the ball with a constant “bentness”.

Most students were really successful, though the pinball projectile group had some trouble…

##expdesign ##graphing ##physicsfirst ##capm

Trend Line Suggestions?

In one class today, we had a discussion about how to think about making a useful trend line. It seemed like a natural place to go in our conversation, but it might have been premature.

Students made a lot of suggestions, some of which I thought were useful and some not so much… But once I started to write them down, I had a hard time NOT writing any down without seeming like I was shutting down the idea. For example, I don’t like the idea that students would be picking one arbitrary point that the line should go through… What’s special about that point, anyway?

Another teacher told me that he drew a bunch of collections of points on unlabeled axes, and students tried fitting lines, THEN discussed it. This seems so, so much better that I want to make a simple practice sheet with a bunch of different distributions of points. Students would work through them, and then we’d be able to decide on the simplest suggestions that seemed useful. (I’d have Logger Pro files prepared for each example, easily accessible.) This would focus the conversation more on identifying patterns, and less on blindly following specific rules and procedures.

For next year!!

##physicsfirst ##expdesign ##graphing ##setbacks

Useful Graphs Practice Sheet

I posted about this practice sheet last year, but since my photos from last year were all lost when the Posterous platform went dark, I figured I’d post about it again!!

I made the worksheet in order to promote a discussion about what type of graphs made sense to create from our data, rather than just declaring which graphs should be made. Each of the graphs shows the same data, displayed differently. On the back of the sheet, students make observations about the graphs, then weigh in on which of the graphs they think is most useful for making predictions.

In ninth grade, students have a variety of opinions on this. Graph A is really attractive, and it’s easy to see how many marbles each bridge supported. Graph C conveniently “has a slope of 1,” as a student said today. Graph D seems to better show the change from one point to another, which would be really important for making predictions if we believed that this wasn’t just due to variability in the phenomenon.

At the beginning of the discussion, we vote on who thinks each graph is most useful for making predictions, then we talk about it. It may take a few rounded but eventually we come around to consensus that best fit lines are very handy when predicting values! Those bar graph lovers can be pretty persistent, though. One student voted for the bar graph twice, but when I asked him how he used the bar graph to make predictions, he said that he’d actually used the best fit line!!

##expdesign ##physicsfirst ##graphing ##practice

Consensus Notebooks and Defining Variables

Today we finally passed out the Consensus Notebooks I prepared for students to take notes in. This is what’s emerged from a long journey trying to find a way to facilitate better note taking in a class that’s so discussion-centered.

The notebook is broken up into topics (cvpm, etc.) and sections, with prompts of questions that need to be answered by consensus. There’s space for example problems, etc. but we have to decide as a class which examples from whiteboarding we want to include.

The first section in the notebook asks two questions – How can we tell which is the independent variable in an experiment? How can we tell which is the dependent variable? These questions were part of the homework practice sheet, and students were primed for the discussion. We talked for a while about which wording would be most useful, during which some students started to write down wording that made sense to them. Eventually, everyone had something in their notes, but it’s up to them to make sure it’s useful.

We also had a good conversation about when we can draw conclusions, and whether we should be surprised by variability in our data. A few sample whiteboards from this discussion:

##expdesign ##consensus ##physicsfirst ##whiteboarding

Pasta Bridges Data Collection

I’m feeling really good about the pasta bridges work this year. Students are being very careful with their work, and there’s a lot if creativity in the room. A few groups were very attached to comparing different types of pasta, which I encouraged. It’ll give us a chance to talk about why quantitative data is important for making predictions by extrapolating with a best fit line.

I used to think that the pasta bridges lab was awesome because of the robustness of the analysis, but with some groups their data won’t be very useful for analysis unless I step in and tell them what to do. Instead, I’m feeling like its useful because there’s just enough variability, and many things to do that AREN’T so useful. It’s difficult to see the variability in your results unless you repeat a measurement with multiple trials. Too many pasta strands make a bridge unbreakable, so it’s unwise to plan out all the values you’re going to try ahead of time. This group, for example jumped from 5 to 10 strands of regular spaghetti:

They couldn’t add any more marbles to the cup, so I tried to encourage them to think about other ways to modify the situation. But then, in trying to show them how strong their bridge was, I ended up pushing down with a finger and breaking the whole thing!!

That many marbles in the cup when it hit the table broke the whole tumbler… I’d thought it couldn’t be done!!

##expdesign ##physicsfirst ##setbacks

River Crossing

In AP, we started working with velocity and displacement vectors in two and three dimensions. I asked pairs of students to prepare a treasure map for finding an object that they left somewhere in the school. They had to describe a starting point and two or three positive directions perpendicular to each other. Then they described three displacement vectors using either components OR magnitude and angle.

This was good trig practice, and they sort of adjusted their difficulty to each other. We ended up spending most of a double period on it, but it was worth it.

Students who finished early solved this simple little problem, then tested it with constant velocity buggies. An amphibious vehicle needs to travel directly across a river that’s moving at a constant speed. At which angle must the vehicle point?

Students made calculations, the tried it out with real stuff. The funny thing about this is that the buggy actually turns when it passes onto the moving river, so the angle the students chose isn’t actually the angle it’s traveling while on the paper. (Also, the paper slows down when the buggy is on it, so it’s important to measure the river speed with a buggy already sitting there.) Thinking about it more now, I’m a little confused why it worked so well… I’ll have to take another look at it later, maybe when we get to refraction!!

After a few groups tried it out, a student mentioned a simulation of a boat reaching an island that’s a similar but more difficult problem. Perfect!!

Here’s a link to the sim:
http://bit.ly/boatislandvectorchallenge

##cvpm ##vectors

Preparing for Pasta Bridges

We got a chance to review the setbacks and progress that we experienced during the marshmallow challenge, then moved on to talking about some science!

We’re starting with the pasta bridges as an example of how to investigate a relationship. We talked for a bit about what we mean when we refer to an “experiment,” and one class was more open than the other to thinking of basically anything as an experiment. If we want our experiments to reveal interesting relationships, however, we need to do some careful planning.

Students identified a number of variables that we could change or measure about the pasta bridges situation. We’ll start investigating the relationship between “bridge thickness” and “maximum load” next class!!

##expdesign ##physicsfirst