Days 89-92: Waves & Momentum Practical

We had a four-day student week for a professional development day on Friday.

AP Physics 1: Waves

This week week we worked on developing and using the wave equation, as well as a few other concepts on mechanical waves. We started with a standing wave lab in Pivot Interactives. On a few labs this year, students haven’t taken the time to get good quality data, which has made it tough to make sense of the slopes during the board meeting. As students are getting better at constructing new ideas from lab results, they are starting to really see the value in having good results to discuss and this lab was a place I saw it really pay off. Students worked through linearizing their graphs and figuring out units of their slope with very little intervention from me partly because they knew those steps would help their sense-making and partly because they are getting more skilled and need less support. Every group had beautiful data for the board meeting and, as we worked on problems later in the week, I heard a lot of students referring back to their graphs or their qualitative observations to think through a problem. All around, this was a really fun week to watch and listen to my students.

Physics: Momentum Transfer Practical

Students worked on applying conservation of momentum to problems, including a lab practical. For the practical, students had to determine an unknown mass using photogates and a dynamics track. The groups that were able to sketch momentum bar charts that matched the collision they decided to do were typically able to find their mass pretty quickly, but a lot of students struggled to connect their bar charts to what was happening on their lab table. As we move into energy, I need to think about how I’m going to make sure students are connecting representations like bar charts to things they can observe or interact with in the lab and beyond. I did enjoy seeing the different approaches groups took to the practical. One based their approach on cart explosion lab and added mass to their empty cart until both carts had the same velocity after the explosion.

Days 85-88: SHM Representations & Momentum Card Sort

AP Physics 1: SHM Representations

This week was mostly about working problems for simple harmonic motion. I kept the focus on representations, including free-body diagrams, energy bar charts, and motion graphs, which made it a good review of a lot of mechanics topics. I also was really pleased when a student was checking out the topics we have left to cover on the AP Physics 1 Your Course at a Glance and asked if our unit on mechanical waves will have anything to do with the simple harmonic motion we’ve been working on.

Physics: Momentum Card Sort

This week, we worked on transitioning to calculations with conservation of momentum. We started with a collision lab from the Modeling Instruction curriculum, then did Kelly O’Shea’s momentum representations card sort. I’ve had a lot of students asking for me to do example problems before they work problems on paper, which I try to avoid. The card sort seemed to fill that need for a lot of students, while keeping the focus on their sense-making. I definitely want to work on a similar card sort for energy.

Days 80-84: SHM Labs & Momentum Bar Charts

AP Physics 1: SHM Labs

We worked on labs to determine what affects the period of objects in simple harmonic motion. I had half the class experiment with pendulums, while half the class used springs. During the board meeting, we did a lot of jumping back and forth between the two experiments; this lead to some good discussion about energy when we saw that mass mattered for the springs, but not for pendulums. I had each spring group use a spring with a different spring constant, which also lead to some good discussion about why the pendulum groups all got the same slope on their linearized graphs, while each spring group got a different slope.

Physics: Momentum Bar Charts

This week, we developed conservation with cart explosions, then worked on using momentum bar charts to represent conservation of momentum problems. After last week, I spent some time talking about the purpose of giving students time to work all (or most) of the problems on paper and warned them I would be unhelpful when they were preparing their whiteboards, then held to it. When we got to mistakes whiteboarding, I required groups to make at least one of their mistakes in the bar charts. While students were working on paper and preparing their whiteboards, I saw a lot more small-group discussion than usual, both within groups and across groups, which was fantastic. During the whole-class discussion, I also got some students speaking up who are usually pretty quiet and one of my classes even got some really good student-to-student exchanges, which have been very rare this year. On Friday’s quiz, students consistently felt really good about their performance. I’m hoping that the positive experience students had whiteboarding these problems coupled with good performance on the quiz will move the class culture in the right direction.

Days 75-79: Projectile Problems, Impulse, & Risk Taking

AP Physics 1: Projectile Motion & Free Fall

This week, we worked on problems and calculations for projectile motion and free-fall. A lot of students were rusty on velocity vs. time graphs (like we haven’t used them much in a while or something!), so it was helpful to revisit. I also continue to really like projectile motion as a wrap-up to linear mechanics since we had a chance to revisit pieces of each major topic so far. I was out sick for a day, which made it tough to fit in the practical I usually do while staying on track for pacing. I think the practical could be good for a review in April, especially since I’ve got some ideas for extensions to connect the lab to more concepts.

Physics: Impulse Problems & Risk Taking

We spent most of this week working problems using momentum and impulse and discussing them with mistakes whiteboarding. This week, I was particularly aware of two common behaviors during problems and whiteboarding that suggests students are still wary of taking risks in my classroom. First, when working the problems on paper, I had a lot of students who got off-task if I wasn’t at their table and were really resistant to sharing their thinking if I was. Second, most of the mistakes students picked for mistakes whiteboarding were in parts of the problems that relied on familiar representations, like vector addition diagrams and velocity vs. time graphs, rather than in the new material.

Recently, I had a conversation with an administrator about classroom environments that encourage academic risks and we agreed that before students can take a risk, they need (1) to feel safe and to know the stake are low and (2) a clear sense of how they will benefit or what they will gain, ideally regardless of the outcome. I’m pretty sure I need to put in work on both of those criteria. Some students who I know really appreciate the discussion that comes from mistakes on new material stuck to mistakes on the familiar content, which tells me they aren’t feeling as safe as I ‘d like. Several of the students who were off-task doing problems on paper find the whiteboard discussions extremely valuable, so I think they just didn’t see a benefit to taking the risk or effort of working through their confusion when we were still on paper. All of this tells me I need to keep working to make sure both requirements for academic risk taking are present in my classroom.

Days 73-74: Projectile Video Analysis & Cart Catching

We kicked off 2020 with a two-day week. Even with the short week, my students fell pretty easily back into classroom routines.

AP Physics 1: Projectile Video Analysis

I like wrapping up linear mechanics with projectiles since its an opportunity to apply pieces of just about everything we’ve learned so far this year. We spent a day on a problem from Michael Lerner representing an orange in free-fall a bunch of different ways. Then, we did some video analysis of tennis balls. In the past, we’ve had to go to a computer lab to do video analysis, so I provided students with a video. This year, since laptop carts are a more practical option, I had each group record their own video. I’m hoping that comparing graphs from different videos will lead to a richer discussion when we have the board meeting next week.

Physics: Cart Catching

To introduce momentum, we did a lab from Scott Lotze, the other physics teacher at Tartan, and had students catch a cart at the bottom of the ramp, then find as many ways as possible to make the cart harder to catch. This lead to an operational definition of momentum and nicely illustrated that both mass and velocity of the cart matter. A few groups tried the plunger carts and noticed they are usually easier to catch, which lead nicely into impulse on Friday.

A hand catching a cart at the bottom of a ramp

Days 58-62: Card Sort & Momentum Bar Charts

This post has ended up a few days late. But I still have yet to miss an intended post on this blog!

Physics: Unbalanced Forces

Students did the classic Newton’s 2nd Law lab with a half-Atwoods machine, then we started fitting net force with the diagrams we’ve been working on. The first set of problems we typically do is just sketching diagrams. This year, we decided to try turning it into a card sort, which I think really helped students who were new to me transfer their knowledge of force diagrams into my classroom, something I’d been thinking about leading into the term. I also pushed using motion maps with acceleration arrows much harder than I have in the past, and one of the results was I got almost no questions this week about which direction the net force should be in.

A set of cards with descriptions of a scenario, free body diagrams, vector addition diagrams, and motion maps

AP Physics 1: Conservation of Momentum

We wrapped up the momentum transfer model (at least for now) by working on conservation of momentum. Students were very excited about Michael Lerner’s watermelon on wheels problem. Aside from being silly, I really like that it pushes students to play with viewing a single scenario with multiple different perspectives. We also did a little bit with momentum bar charts, since they show up in the AP Physics 1 workbook we did a few problems out of, and I found they really helped a lot of my students. I need to make much more use of those bar carts next year.

Day 72: Tests

Today was our last day of class before winter break. In all three of my classes, we wrapped up a topic by taking an assessment.

AP Physics 1: Energy Bar Charts & Unbalanced Forces

I’ve been giving students at least two in-class opportunities on every learning target this year, so this assessment covered energy bar charts and revisited unbalanced forces. Almost everyone improved on unbalanced forces, which is exactly what I want to see!

Physics: Conservation of Momentum

Students took their conservation of momentum test. Students have been saying the bar charts make the math very intuitive, and it definitely shows on the work I’ve graded so far. This is definitely the easiest time I’ve seen students have with momentum.

Chemistry Essentials: Density

This assessment was more hit or miss than my other classes. I had some students who did great, but a few were surprised to see some representations, like particle diagrams and a mass vs. volume graph, that were significant components of our daily work. I’m thinking about doing some individual conferences with students after break to try to get a better understanding of what’s behind that.

Day 71: Unbalanced Forces Practical, Mistakes Whiteboarding, & Density Practical

AP Physics 1: Unbalanced Forces Practical

Since tomorrow’s assessment will include a second shot at our unbalanced forces learning target, we did a practical where students used unbalanced forces and constant acceleration to predict the velocity of a cart after it traveled a certain distance down a ramp. While we haven’t really dug into energy calculations yet, I did encourage students to try doing it as an energy problem if they had time, and the groups that tried it were excited to see the same answer two different ways.

ap practical

Physics: Mistakes Whiteboarding

Students did mistakes whiteboarding to go over yesterday’s problems; not surprisingly, it went very quickly. I also didn’t have to get on students’ case about units or well-labeled diagrams, since they are at a point where they find it useful to see and were asking each other for that information when someone left it off.

I noticed a couple of groups in one section had started some interesting notation for their unknown I haven’t seen before; students really, really like to use x for their unknown, which I push back on, but these groups were using x plus a unit for their unknown. I can’t quite decide whether I like it; using x as an unknown does get in the way of using x to represent position, so I know I’d rather they use the standard variable. On the other hand, seeing the units written out for the unknown helped a lot of students see what math they needed to do and the students I talked to were very clear that “x m/s” represented how many meters the object traveled for every second, which the students just using v were not as consistently clear about. I’m trying to decide whether the potential value here outweighs the hurdles it may cause down the line; one option is to let them leave the units, but push they should still use the standard variable (like “v m/s” here). I don’t see myself ever introducing this kind of notation, but I’m also not sure I need to get students away from it if they find it useful.

phys mistake (1).jpg

Chemistry Essentials: Density Practical

As a practical to wrap up the density unit, I asked students to plan an experiment they could use to answer either whether the shape of an object impacts its density or whether the volume of an object impacts its density. It went about as I expected; initially, students were uncomfortable with how open-ended the task was, but, once they got started, they moved forward easily with the task. I think the challenge had more to do with students’ discomfort with this kind of task than their ability to complete it.

chem prac

Day 70: Systems and Bar Charts, Conservation of Momentum Problems, & Pivot Interactives

AP Physics 1: Systems and Bar Charts

Students worked on whiteboarding some problems switching between different systems for energy bar charts. Students were doing a nice job of switching smoothly between different systems.

ap bar chart

Physics: Conservation of Momentum Problems

Students worked on calculations with conservation of momentum. This is the first year I’ve really used momentum bar charts, and its also the first time I’ve had students call conservation of momentum easy. The best part was I overheard a lot of students talking about whether their answer was reasonable based on their bar charts. When one of my AP sections came in, I still had some bar charts on the whiteboard and my AP students asked why I didn’t teach them momentum bar charts since it made the problem seem much easier. I’m sold and will be bringing bar charts into AP next year.

Chemistry Essentials: Pivot Interactives Density

I am as part of Pivot Interactive’s¬†Chemistry Fellows¬†program.

Students worked on an activity in Pivot Interactives to identify materials based on their density. I ended up giving students a handout to record their work, rather than having them answer in Pivot’s interface, since something about writing on paper seems to feel more comfortable for a lot of my students. I was really excited about how many students on their own tried to decide between multiple materials with similar densities by paying attention to what they could see about the material. It was also nice to be able to easily split up the class to look at different liquids so we can have some conversation tomorrow about who should have similar answers and who should have different answers, and why.

pivot density.PNG

Day 69: Mistakes Whiteboarding & Card Sort

AP Physics 1: Energy Bar Chart Mistakes Whiteboarding

Students did mistakes whiteboarding with energy bar charts. There was some good discussion about what differences matter in energy bar charts at this point and what differences, like the exact number of boxes, are irrelevant.

ap bar chart.jpg

Physics: Momentum Card Sort

Students worked on a momentum transfer model card sort I got from Kelly O’Shea. I was (pleasantly) surprised by how easy it was for students to work out which equation went with each problem. The force-time graphs in the card sort were tough; part of the trick is those graphs are more similar across different problems than some of the other graphs and we haven’t made enough use of force-time graphs in other contexts for students to focus on the subtle details that distinguished the different graphs here.

card sort.jpg

Chemistry Essentials: Density Mistakes Whiteboarding

This class also did mistakes whiteboarding, but on a worksheet using different representations for density. There was some great discussion and some signs this group is starting to build an identity as a class, which is great.