Days 80-84: Impulse & Bouncy Balls

Around mid-day last Friday, we found out enough staff were out (almost all with COVID) that we would be remote this week. Monday was an asynchronous day so that teachers could post an assignment, then spend the rest of the day planning for the rest of the week. The rest of the week was synchronous following our usual bell schedule. We were required to have some synchronous instruction at the start of each hour, but were encouraged to make the rest of the hour something that students could do away from Zoom. In both my courses, I stuck to activities that should be doable in class time, but made them due at midnight rather than the end of class. I got really positive feedback from students since that gave them the option to take a break from their screen and do their physics later, especially for my classes in the middle of the day. That also meant I had time to look over their work before school and make some adjustments to the instruction I’d planned for the day. I think being transparent about how student work was informing my instruction also helped with work completion, since it gave students a clear reason to at least attempt the work on the day it was assigned.

Near the end of the school day on Thursday, we found out that next week will be remote, as well. Next week, I want to keep the same general structure since that seemed to work well for both me and for my students, but I want to try and get a little more student-to-student discussion.

Physics: Impulse

Our plan this week had been to introduce momentum and impulse. We normally start with a cart catching activity, where students find as many ways as possible to make it harder to catch a cart. That translated fairly well to an asynchronous lesson for Monday where we asked students to brainstorm ways they could change how difficult it was to catch a ball during a game of catch. I put all of the responses onto a Jamboard and did some sorting, which lead very nicely into a definition of momentum as well as the idea that force can chance momentum.

The rest of the week we relied heavily on Pivot Interactives (disclaimer: I work for Pivot Interactives writing activities). We started by introducing Newton’s 3rd Law, which we’d decided to save for momentum this year since that’s when students seem to do the most interesting and useful thinking with it, then did an activity where students evaluate two competing claims about what is transferred in a collision between two gliders on an air track. We haven’t done many of those kinds of questions this year, so students needed some support in figuring out what kind of evidence they needed, but it was mostly a matter of keeping them focused on the claim and not overcomplicating what to collect. The bit that got a little rocky is I tried to go from there to the impulse equation, which just didn’t flow naturally. I’ve thought about changing my momentum storyline to start with conservation, then narrow our focus to the individual objects that make up the system to look at impulse. In retrospect, a part of me wishes we’d made the leap when we switched to remote instruction since I think that storyline would have flowed better with the resources available to us, but sticking with the storyline we’d already planned took less thinking and will likely make for a smoother transition when we get back to in-person instruction.

AP Physics 1: Bouncy Ball Energy

As part of my energy unit, I’d planned to do an activity (shameless plug for my article on this activity in The Science Teacher) where students use video analysis to decide whether a bouncy ball dissipates energy primarily due to air resistance or due to the impact when it bounces. The hard part of this activity is prior to the video analysis, I have students do some whiteboarding where they sketch representations including LOL diagrams, free-body diagrams, and velocity vs. time graphs for the bouncy ball-Earth system first assuming only air resistance dissipates energy, then assuming only the impact dissipates energy. I ended up using a version of this activity I wrote for Pivot Interactives that replaces that whiteboarding with multiple choice questions. I have struggled this year with helping my students effectively use diagrams as thinking tools, so I think having them choose from a set of diagrams was a useful scaffold. I had the questions set to autograde, which made it easy for students to progress asynchronously, but I think some good discussion could have happened if I’d turned off autograding and instead had students use our synchronous time to discuss their answers and come to a consensus.

Days 75-79: Values and Beliefs & Elastic Potential Energy

This week has felt a little weird. Coming back from break, we’d gotten some messages to be ready to shift to virtual learning and all week the number of students and staff out went up, so everyone felt like we were in limbo. Near the end of my teaching day today, we got word that next week will be remote.

Physics: Values & Beliefs About Physics Learning

We started this week with a version of the values and beliefs lesson from Kelly O’Shea. There wasn’t as much discussion within groups as I was hoping (and it probably didn’t help that I was giving groups more space than usual to try and reduce my COVID exposure), but students had some great insights and really interesting things to say on the individual reflections I had them complete. One thing I felt like was missing in how I implemented this was some conversations about the costs and benefits of different views of physics and physics learning. One of the last things I had students do in their groups was pick some values or beliefs they think we should aspire to, and a lot of groups said we should aspire to do a better job of valuing memorizing facts and equations. I wonder if giving more space to why certain values and beliefs are or are not given a space in a particular classroom would have helped with some conversation about why they see memorizing as important and whether that is compatible with our classroom.

After two days of that, we spent the rest of the week on some problems about pushing cardboard boxes based on problems in Matt Greenwolfe’s More Models in Modeling materials. My goal was to refresh students on velocity vs. time graphs and free-body diagrams before we dive into momentum. There was a lot of great discussion, with lots of animated arguments. I was also really pleased at how often I could have students simply add a diagram, such as a system schema, to identify and fix their mistakes. I still need to work on how to facilitate a good whole class discussion with these problems, but I think part of the issue is I approach these problems with what I call consensus-building discussions, where I have every group whiteboard the same problem, then we try to resolve differences, but I don’t do this type of discussion very often so students don’t have much practice with it.

AP Physics 1: Energy

This week, we focused on going from LOL diagrams to doing calculations with conservation of energy. We started by doing a lab to find the equation for spring potential energy, which gives us all of the major energy types, then did a card sort that included equations based on just the types of energy and equations based on measurable quantities like velocity, mass, and height. The card sort made for a very nice bridge between the two types of mathematical representations.

Days 72-74: Unbalanced Forces & Kinetic Energy

We had a short 3-day week to lead us into break.

Physics: Unbalanced Forces

We wrapped up unbalanced forces this week with a lab practical. I put a cart on a ramp, held in place by a string attached to a force sensor. Students had to first predict the tension in the string and next predict the time it would take the cart to travel between two photogates on the track once I cut the string. It was trickier than I expected for students to recognize that the tension in the string would be the same as the net force on the cart once the string was cut. Since that was an important idea in the paradigm lab we did this year, I left students to figure out that point on their own, but I think it would have been worthwhile to give students some questions or other structure to think through that aspect of the practical. We haven’t revisited velocity vs. time graphs lately, so I was very excited to see how well they did annotating their graphs and setting up equations to find the time.

A cart on a track with two photogates. The cart is tied with a piece of string to a force sensor and is held in place just before the first photogate.

AP Physics 1: Kinetic Energy

Students used Pivot Interactives for a lab to find the mathematical model for kinetic energy. Their data came out beautiful, but the introductory section of the activity didn’t do as much as I’d hoped to prepare students to collect data. This fits with a larger pattern I’ve noticed this year where students in both my courses don’t seem to make a clear connection between the pre-lab discussion (which the introductory section was similar to) and the actual lab. I think I haven’t helped students make a clear connection between the experimental design thinking we do in those discussions and what they will actually need to do in the lab. I’m giving some thought to how I can do a better job of showing how those discussions lead naturally to what students will be doing in the lab.

A silicone puck is levitating over a curved magnetic track. The puck is held in place near the top of the track by a small block of wood.

Days 62-71: Unbalanced Forces & LOL Diagrams

I think last week is the first time I missed a post on this blog. The end of my grad school semester plus the usual challenges of the Thanksgiving to winter break stretch got the best of me.

Physics: Unbalanced Forces

Last week, we did a paradigm lab for unbalanced forces. I was really dreading the classic half-Atwood machine, so tried a lab Kelly O’Shea suggested. We set up a ramp, then used a string to connect a cart to a force sensor. Next, I cut the string and students observed that the cart accelerated down the ramp. Students were able to reason out that the tension in the string before it was cut must match how unbalanced the forces on the cart are after the string is cut. Students also were quick to recognize that we could change the tension in the string by changing the angle of the ramp. Students then went and collected data to find a relationship between the size of the unbalanced force and the acceleration of the cart. Compared to the half-Atwood, students had a much clearer conceptual understanding of the lab and the data was much cleaner, so I will be sticking with this approach.

A Vernier sensor cart on a ramp tied with a piece of string to a force probe held in a person's hand

This week, we introduced problems by starting with a card sort where students matched a situation to the motion map, free-body diagram, and vector addition diagram. The acceleration arrows on the motion maps seemed to help students with thinking about the direction of the net force, though a lot of students needed some prompting to use the motion maps. I think that is because they haven’t been a very meaningful sensemaking tool in my class before now. If I want students to be ready to use them with unbalanced forces, I need to give some thought to how I’m going to push students to make meaning from motion maps when they are first introduced.

Purple cards in four piles. One pile has text describing a problem, one pile has motion maps with acceleration arrows, one pile has unlabeled free-body diagrams, and one pile has unlabeled vector addition diagrams.

AP Physics 1: Conservation of Momentum & LOL Diagrams

Last week, we worked on conservation of momentum. I introduced momentum bar charts so we could do some problems from the College Board’s AP Physics 1 workbook. They seemed to really help students, so I wish I’d introduced them much earlier. Students ended up not making much connection between the problems we’d done earlier and the momentum bar charts, so I think I needed to introduce the bar charts right off the bat. The quiz didn’t go as well as I would have liked, but next week’s quiz will include a retake. I’m thinking about what I want to build into class next week as a way to address the gaps I saw on the quiz.

This week, we’ve been focused on energy bar charts and LOL diagrams. We did a lab I’ve done in the past where students raise a cart to the same height above the table using ramps of different angles to see the force vs. distance graph always has the same area. After that, I defined the major forms of energy we’ll be dealing with and students practiced drawing energy bar charts, including for situations where they switch between systems. These are coming really easily to my students and we had some great discussions using mistakes whiteboarding on some bar chart problems. The big challenge will be helping my students revisit these ideas after break.

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 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.