Days 58-61: Vector Addition Diagrams & Impulse

This week was the start of a new trimester for us.

Physics: Vector Addition Diagrams

At the end of last trimester, we were working on balanced forces, but had only done situations where all of the forces were completely vertical or completely horizontal. This week, we started working with balanced forces where at least one is at an angle. This year, students have been struggling to relate different representations and see the connections between system schema, free-body diagrams, and vector addition diagrams, so I tried to keep my focus on supporting those connections. We started with some mini-practical stations I got from Kelly O’Shea to remind students of what we’d been working on before Thanksgiving break. When students asked for help, I made a point of emphasizing how the representations they’d drawn already to show how it lead to the next diagram. Next, we did an activity from Casey Rutherford where students used pipe cleaners to make the arrows from a free-body diagram, then physically rearrange them to make vector addition diagram, which I think helped solidify those connections. During the stations, I noticed that when there were multiple upward forces, a lot of students were drawing the arrows curved, which I think contributed to them struggling to connect the diagrams. Doing an activity where they were already given the free-body diagram and all of the arrows were perfectly straight seemed to help. We wrapped up the week with some paper and pencil problems relating free-body and vector addition diagrams (also from Kelly O’Shea). Students seem to be getting the hang of how these representations are related, and were starting to work on the next problems in their packet where we add in calculations before I assigned them, which was really exciting!

AP Physics 1: Impulse

Before finals, my AP students were working on impulse, but we ran out of time to assess it. This week, I decided to start by revisiting impulse and taking a quiz over it before we move on to conservation of momentum. We focused on some problems from the AP Physics 1 workbook, some of which included momentum bar charts. I usually skip over momentum bar charts, but my students seemed to find them really useful, so I think next year I want to make them more central to my momentum transfer unit.

Days 51-55: Final Review

We are almost at the end of the trimester! Both classes wrapped up a topic, then started reviewing for the final.

Physics: Constant Acceleration & Balanced Forces

Students worked on a packet of problems. One nice thing is many students were working more independently than usual, so it was easier for me to give more intensive support to students who’ve been struggling. It was really great to see how many students had moments where something we’ve been working on finally clicked.

AP Physics 1: Model Summaries

We started the final review with model summaries, where each group takes a model from so far this year and prepares a whiteboard with the major representations including graphs, diagrams, and equations. My students didn’t have as strong a positive response this year as in the past, and I think that is probably related to some conversations I had this week where students weren’t aware that this class is organized by models. This tells me I need to get more intentional about using that language if I want students to think in terms of what models we have.

Days 46-50: Force Labs & Impulse

Physics: Force Labs

This week was the force of gravity lab and the spring force lab. Students have been struggling to draw meaning from labs, so I spent more time than usual on “translating” the line of best fit into physics and on the conclusions portion of our lab template for the gravity lab, which seemed to pay off. On the spring force lab, I tasked students with doing that more independently and encouraged students to use their force of gravity lab for reference. I noticed a lot of groups using Fg, rather than Fs, and N/kg as the slope unit, rather than N/cm, which tells me students were focusing on what the right answer was in the force of gravity lab, rather than why it was the right answer. This fits with some other observations I’ve made this year and tells me I need to keep thinking about how to get students focusing on their process in labs, rather than what should be the correct result.

The other physics teacher and I decided to use the spring force lab to introduce force sensors since we have some more involved labs coming up where they will need to use force sensors, and I was really pleased with how quickly students got comfortable with those as a tool. I think it was really valuable for students to have their first exposure one where the measurements were relatively straightforward. I tend to fall into using low-tech tools until there is a good reason to use probeware, but the downside is students are then learning to use the probeware in labs with relatively complex scenarios or when they need to use multiple probes to measure different things. I need to remember the value in starting to use probes in relatively simple labs where we don’t strictly need the probeware.

AP Physics 1: Impulse

This week we introduced momentum and impulse. We started with the Modeling Instruction cart explosion lab where students launch spring-loaded carts off each other and graph the ratio of the cart’s velocities vs. the ratio of the cart’s masses and establish the idea of momentum. Next, we did video analysis of two linked air pucks to introduce center of mass (based on an article in The Physics Teacher by Taylor Kaar, Linda Pollack, Michael Lerner, and Robert Engles). After that, we looked at the change in velocity of carts as they crashed into force sensors with hoop springs to introduce impulse. I’ve tried a few versions of that lab and have yet to have students collect satisfying data, so have been thinking about what I want to try instead. In the course of my thinking, I realized I don’t think I’m satisfied with the storyline of my unit. I like the cart explosion lab to introduce momentum and the center of mass piece to think about what it means to treat an object as a particle, but I think those activities lead more naturally into conservation of momentum than impulse. I think next year I want to try starting the momentum transfer model with the same two activities, but then go straight into conservation of momentum. One route to impulse from there could be asking what if we change the system, such as looking at just one cart at a time in the cart explosion lab to motivate new tools in our model.

Days 43-45: Forces

We had staff development days on Monday and Tuesday, so this was a short week. I know my students really appreciated the four day weekend with how drained they’ve been feeling and it was helpful to me to have two days that were a big change of pace.

Physics: Force Diagrams

This week we focused on drawing system schema and free-body diagrams. Since students have been struggling to find meaning in our labs this year, I was much more conscious than usual of explicitly raising activities from last week when helping students or giving instruction. That seemed to help students see how what we’d done in the lab related to what we were now doing on paper and started referring to the labs themselves. I had a few students who got frustrated very quickly, so I think I need to work on making more explicit that I rarely expect students to see a problem and immediately know the answer, instead I expect them to work through piece by piece. I had some success keeping some students who’ve been very frustrated from shutting down by starting with what is correct on the work they’d already done. Those students haven’t always had work I can refer to yet when they are getting frustrated, but it is both unsurprising and important to keep in mind that it is helpful for students to know that they are doing some things right before we talk about where they are stuck.

AP Physics 1: Unbalanced Force Calculations

Students worked on some problems for unbalanced forces, including a mix of math-heavy and writing-heavy problems. They are getting better at work through calculations, but had some trouble seeing diagrams on a useful tool on more conceptual problems. Forces are where I think the usefulness of diagrams as a reasoning tool really starts to shine, and this just shows we haven’t done as much practice as usual with the kinds of problems where that is really useful. I need to make sure that we get some of that practice in so students can start seeing how they can use diagrams to support their thinking.

Days 38-42: Forces

Physics: Balanced Forces Intro

This week we started balanced forces. Since making sense of labs has been really challenging for students this year, I put a lot of thought into how I wanted to frame the lab activities. We started with the bowling ball and mallet lab, where I really emphasized the motion maps to draw connections between forces and what we’d already been learning. In the past, I’ve had some groups who record what they expect, but never actually try tapping the bowling balls with mallets. To prevent that, when I introduced the lab, I emphasized that I am not expecting students to know what will work and that this lab is about observation, not prediction. Motion Shot is still working on my phone, so I used it to help convince some groups that a bowling ball moves at a constant velocity without any interactions, but I wish I’d pulled out the app for every group that was struggling with drawing motion maps; I think that did a lot for the groups I used it with to connect what was happening in the classroom to the more abstract representation. We followed up with some interaction stations based on Brian Frank’s introduction to forces, which I again introduced by taking more time than usual to talk explicitly about the purpose of the activity and what I expected students to know.

AP Physics 1: Unbalanced Forces

This week we started unbalanced forces with the modified Atwood’s machine. We used Vernier motion encoders to collect the data, and I found students were pretty overwhelmed by the technology. It occurred to me that this was their first experience using force sensors and they’ve only used the motion encoders once before. The lab took longer than I’d hoped, though students still got reasonably good data. I think next year I need to plan to get out these materials for some of the simpler labs where I default to using tools like spring scales with the mindset of getting students practice with the probeware before labs where the data collection is more complex. I’ve done that in the past, but am a little out of practice on teaching students lab skills!

Days 35-37: Lab Practicals

The Minnesota teacher union has our convention on this week, so we only had school Monday through Wednesday. I think staff and students alike are feeling pretty run down, so this is good timing for everyone to take a break.

Physics: CAPM Practical

This week, students worked on the “catch the loot” lab practical for constant acceleration. After how smoothly paper and pencil problems went last week, I expected the practical to go very smoothly, but students really struggled. I also found a lot of groups were not interested in testing their calculation with the materials. I think I underestimated how difficult it is for my students to draw connections between what happens in the lab and what happens on paper. I teach all of my physics sections in the morning, so when my colleague who teaches physics in the afternoon saw how challenging the practical was, he added a brief whiteboarding activity to help bridge the paper and pencil problems to the practical, which seemed to really help his classes. Going forward, I need to make sure I plan how I will help students make better connections between what happens in the lab and what happens on paper.

Students also had their quiz over constant acceleration calculations this week and many of my students were really worried after having their confidence shaken by the lab practical. On the quiz day, I took the first half of the class to have students whiteboard a word problem, which they were able to nail with minimal help from me and seemed to really improve the tone of the class before the quiz. I shared my reasoning for doing that problem, and a student made sure to tell me how much she appreciated that I am paying attention to where they are at and trying to adjust to what they need, which was a good reminder that talking about my reasoning for instructional decisions can do a lot to help students feel less frustrated in my classroom.

AP Physics 1: Balanced Forces Lab Practical

Students did a lot of practice with applying math to vector addition diagrams, including a lab practical to find an unknown mass. My students were quick to recognize the math that would be useful, but weren’t always comfortable with how to use the math. I really appreciated the small class size I have in AP since I think that has helped the class feel more cohesive, which has meant students are very comfortable asking each other for help and very willing to patiently work with their peers when asked for help. The small class size has also made it easier for me to step in before students start to experience any serious frustration and has helped me build trust with my students that I will be able to coach them through things if needed. Knowing the positive impact the strong relationships students have with each other and have with me, I need to keep thinking about how I can do a better job of building relationships in my much larger physics classes.

Days 30-34: CAPM Problems & Force Equations

Physics: CAPM Problems

This week was mostly about working problems using the constant acceleration model, which I have students do almost entirely from velocity vs. time graphs. We started with some problems I got from Kelly O’Shea where students are given some velocity vs. time graphs they annotate and write area equations for. Next, we shifted to word problems. I was blown away by how easy these problems were for students. Doing calculations with the constant velocity model had been very challenging for a lot of students, but something really clicked this week. Students were even including units on all of their work with almost no prompting and showing their work really clearly. I’m not sure what it was, but it was nice to have a week where students were nailing what I gave them!

AP Physics: Force Equations

We did labs to find the equations for the force of gravity and for spring force. Most years, my students are most comfortable with mathematical representations and it’s a challenge to get them comfortable with other representations, but this year my students are defaulting to other representations in some really cool ways. At this point in the year, when I have groups make a graph on a whiteboard, they usually default to including an equation for the line of best fit whether or not I ask for it. Instead, my students this year have been writing “for every” statements about their slope unprompted. For example, on the force of gravity lab, every group wrote some variation of “The force goes up 10 N for every 1 kg” on their own. That tells me that my students find the “for every” statements useful and intuitive, which is a great place to be developing physics knowledge from.

Days 25-29: Mistakes Whiteboarding & Free-Body Diagrams

Physics: Mistakes Whiteboarding

This week we did a lot of practicing with constant acceleration diagrams. The highlight was doing mistakes whiteboarding. Based on a recent conversation with Kelly O’Shea, I was much more explicit that the role of the group presenting is merely to facilitate the discussion while the role of the rest of us is to help them get to the right answer. In two of my classes, this seemed to be really freeing for a lot of groups as they presented, and lots of students were quick to ask their peers to justify changes to the whiteboard when they were presenting. There was also some fantastic back and forth where the students who weren’t presenting disagreed about what to change on a whiteboard and had exactly the kind of discussion I’m after with mistakes whiteboarding. In my third section, the discussion was still pretty rough, so I need to give more thought to how I can support them in having deeper student-to-student discussions.

AP Physics 1: Free-Body Diagrams

This week we focused on drawing system schema and free-body diagrams. I was reminded how much I love framing forces in terms of interactions and the discussion that comes out of even the very basic free-body diagram problem set in the Modeling Instruction materials. I love that on a problem about a skater sliding across frictionless ice at a constant velocity, I get to hear students internalize Newton’s 1st Law as they wrestle with what interaction could be giving the skater a forward force. This year, my students also got into Newton’s 3rd Law during the discussion as one student pointed out the ice is pushed downward by the skater’s foot, so the class wrestled with how that impacts the normal force before agreeing that same interaction pushes the skater up and the ice down. We also did Kelly O’Shea’s force diagrams card sort, which I use as students’ first introduction to vector addition diagrams. I was really pleased by how easily they connected the vector addition diagrams to the free-body diagrams and by how they started contrasting balanced and unbalanced force scenarios with minimal input from me.

This year has felt unusually draining so far, but my students are doing some great work in my class and reminding me why this job is worth it.

Days 20-24: Constant Acceleration & Forces

Physics: Constant Acceleration

Physics started constant acceleration this week. We used video analysis to get position vs. time and velocity vs. time graphs for a cart on a ramp, then worked on Kelly O’Shea’s CAPM card sort. This was my first time using video analysis to introduce constant acceleration, and I’m really happy with the results overall.

The big thing I’m thinking about right now is when students are in groups. The first week of school, students were almost timid and weren’t engaging with each other, but tended to stay at their tables, which made it easy for me to pull the full group in when I came to answer a question. Over the past few weeks, things have shifted in a few of my classes. Students are still not engaging much with their groups, but are also leaving their group to go see their friends, which is making it harder for me to gather the whole group when I’m answering a question. I think a lot of it is students are out of practice working with each other after last year and simply aren’t seeing value in staying with their group. I think I need to make much more use of group roles and spend much more time working with students on how to interact with each other and building community so students feel like they can connect with more people in the class.

I think these issues have been compounded by the fact that I have larger class sizes than usual, so I’m juggling 10 groups in each of my classes. That means that if I’m having meaningful conversations with each group, it can be a while between my visits to a given group. I’m realizing that many of my students don’t feel like there is much they can do besides wait for me when they are stuck, which I think is contributing to some of the behavior I’m seeing. I think part of what I need to address is helping students recognize the strategies they have to work through moments of confusion or challenge.

AP Physics: Forces

We started the week with the catch the loot practical, which is one of my favorites since it is a challenging calculation at this point in the year, but so satisfying. This class is only 12 students, so I’ve had a much easier time building a positive class culture and helping students with strategies for when they are stuck. One thing I loved is when the first group finished, they decided each of them should join one of the other groups to help their classmates with the lab practical.

We shifted into forces with some mallet ball followed by Brian Frank’s interaction stations. So far this year, I’ve been really intentional that when we show the shortcomings of a common preconception, I also ask students about what reasonable thinking might lead a person to that idea and explicitly validating that thinking. My goal is to make it so that adopting a new idea doesn’t mean you are wrong or don’t understand physics, it just means you didn’t have all of the information when you formulated your old idea. I saw some payoff with the mallet ball as my students were quicker than usual to let go of the idea that they needed to keep tapping the bowling ball to keep it moving with a constant velocity and talking about the useful aspects of that idea even once they’d adopted a new one. We’ll see next week how that carries over into drawing free-body diagrams.

Days 15-19: Problems & Technology Tools

AP Physics 1: Problems

A lot of this week was working on calculations for constant acceleration. My students are struggling more with the algebra than in a typical year and it sounds like other teachers are seeing similar things. They are doing some great mathematical thinking, but just aren’t as comfortable as usual with common processes like making a quick graph based on an equation or doing algebraic manipulation. I tend to trust that once students see what math they need to do, I can expect them to get through the math without much support. This year, I need to make sure I’m putting attention to helping students develop their math skills alongside the physics. My course on STEM integration theories last fall got me thinking about how I can go beyond math as a tool in my classroom to instead support meaningful math sensemaking, and this year will be a good push to put what I’ve been thinking about into practice.

I also graded the first lab write-up this week, and my students did much better than I usually see on the first lab write-up. In general, this group of students are stronger than usual at explaining their thinking and the kind of writing I usually look for, which is fantastic in a course like AP Physics 1. I’m really excited to be able to help students build their already strong skills.

Physics: Technology Tools

This week, we wrapped up constant velocity by having students do activities with Vernier Video Analysis and Pivot Interactives. For the video analysis assignment, we had students record a short example of something they thought was constant velocity, then use the video analysis results to test the claim. Since the focus of this activity was on interpreting the position vs. time and velocity vs. time graphs, I think it would have worked well when we were preparing to transition from interpreting diagrams to doing calculations to help break up the stretch we had of paper and pencil problems.

A big goal of these activities was to introduce students to tools we’d been using in a context where students were already pretty solid on the content. When introducing technology, I do a minimal demo and instead provide students with a user guide or other detailed instructions on how to use the tool. I have a lot of students who are more comfortable with a walkthrough, so I spend most of the hour on my feet answering questions by reminding students to use the resources I provided them. These days are tiring, but they pay off with students quickly becoming very independent with these tools as they learn to navigate the user guide or help documents. However, I’ve developed some new back issues in the last year and a half and am very aware today that I can’t currently bounce around the room as much as I used to. We are using video analysis again on Monday, and I need to give some thought to how I will balance ensuring students have the support they need and feel like I’m available for questions with managing my own health.