Days 77-81: Projectile Graphs & Cart Explosions

AP Physics 1: Projectile Graphs

This week was all about velocity vs. time graphs for projectiles. We started with some video analysis of videos students had recorded to see what the graphs looked like. Students did a really nice job during the board meeting of connecting the graphs to other key ideas, like the forces acting on the projectiles. I showed students the three views of a projectile video from Pivot Interactives that shows a side view where the full 2D motion is visible, a top view where only the horizontal motion is visible, and a front view where only the vertical motion is visible. Even though we didn’t do an activity with the videos, students referred back to it when making sense of why we had two different velocity vs. time graphs. It was also fun to see more students making connections to derivatives now that they are further along in calculus than when we did motion in September.

Physics: Cart Explosions

Students did the cart explosion lab from the Modeling Instruction materials. They easily picked up on the pattern in the data, but I never feel like the connection between their data and the idea of conservation of momentum is as clear as I ‘d like. I think one trick is momentum doesn’t have a very good conceptual definition and mathematical reasoning has been challenging so far. Once we started working on momentum bar charts, students were doing really well with them and doing a lot of connecting the bar charts to what they’d observed in the lab, which was great!

Days 73-76: Where Does the Energy Go & Math Sensemaking

AP Physics: Where Does the Energy Go

This week, students started working on an activity to figure out what interaction causes energy to dissipate as a bouncy ball bounces (I wrote this up for The Science Teacher a few years ago). After observing a bouncy ball, students agreed that some combination of the impact with the table and the air resistance on the bouncy ball are responsible for the energy dissipating, so now their task is to figure out which it is. I spend a lot of time priming students for what evidence might be useful and we started late in the week, so we mostly focused on making one set of energy bar charts for if only the impact dissipates energy and one set for if only the air resistance dissipates energy using five key points along the bouncy ball’s motion (right as it’s released, right as it reaches the table, right as it leaves the table, at the top of the first bounce, and right as it reaches the table a second time). I forgot to get a picture, but one group did a cool thing where they labeled which interaction was happening between each of their bar charts to help keep track of when the dissipated energy should show up. We then had some good discussion about what these energy bar charts tell us we will actually observe in the lab.

Physics: Math Sensemaking

This week felt a little goofy. The other physics teacher and I are doing the same activities on as close the same day as we can so that we can plan together (a key survival tactic when both of us are also doing what are supposed to be full-time jobs outside the classroom!). He is out this week, so we used several Pivot Interactives activities to wrap up forces and introduce momentum (full disclosure: I work for Pivot writing activities). As I worked with students, two big things that aren’t directly tied to the science content ended up at the front of my mind. First, students told me their biggest frustration with the Pivot activities is they had to measure carefully to get the autograded questions correct. I think this fits with where students believe that physics knowledge comes from. When students see experiments, observations, and measurements as where physics knowledge comes from, I find that students tend to measure more carefully because they see a purpose to having good-quality measurements. Combined with some other things I’ve observed about my students, I think many of them see me as the primary source of physics knowledge in the room, so why should it matter whether they measure carefully?

Second, I saw a lot of evidence that students are not attaching physical meaning to their measurements. This was most apparent to me in an activity where students used Newton’s 2nd Law to determine the mass of an unknown object. Students were able to measure the net force on a system that included two gliders and the mystery object as well as make measurements to determine the acceleration of the system. Once they calculated the total mass of the system, a lot of students really struggled with how to use the given mass of the gliders to figure out the mass of the mystery object. This made me think of the work some of my grad school classmates and professors have been doing around blended sensemaking in science (here’s a taste), which is a term for simultaneously doing sensemaking in science and in math. Recognizing they needed to subtract the mass of the two gliders from the total mass required students to recognize what the mass they had calculated represented, how the given mass of the gliders relates to the mass they had calculated, and what the operation of subtraction represents in this context. Doing all of that can be some pretty tricky blended sensemaking! Realizing how much my students are struggling with this is helping me make sense of some of the other struggles I’m seeing in my class right now. I’m not sure what my fix is yet, but I definitely want to keep thinking about how to support students in attaching meaning to numbers and doing blended sensemaking.

Days 68-72: Energy & Forces

This was another week that was a little messy. I had a sub Wednesday through Friday so I could present some of my doctoral research at the ASTE conference. On top of that, we had an ice storm early Wednesday morning that resulted in a late start, so two of my classes didn’t meet

AP Physics 1: Energy

This week was all about applying our model of energy transfer. We had some great discussions before I left where students were navigating how different systems affect the problem. We also did some TIPERs problems where some common preconceptions came out. The last few years, I’ve been working on being more intentional about making sure we discuss what’s correct about those preconceptions and whether there are other questions those ideas are the correct answer to. My students this year have been really receptive to those conversations, which makes for fun discussions and seems to help kids feel comfortable sharing ideas. Once I left, students worked on an energy lab practical in Pivot Interactives and some energy problems from the College Board’s AP Physics 1 workbook. My students were a little nervous about doing those problems without a teacher who knows the content in the room, but I’m betting they will make some good progress with peer conversations.

Physics: Unbalanced Forces

Students started working problems using unbalanced forces. My students and I are getting more comfortable with each other, which is leading to the discussions getting better. That’s helped me make the connection that the reason some of my students have been struggling with the direction of some forces is they don’t have a great conceptual understanding of the interactions involved in some forces, especially the normal force. I made sure we spent some time reinforcing those ideas by doing some things like using the matter model for normal force and a pair of hairbrushes for friction. My go-to move is to place those on a board at different angles to help students get a visual and tactile hook to make sense of what direction the normal and friction forces should go, which seemed to help a lot of students. We also spent some time looking at how the normal force an elevator passenger experiences connects to the acceleration of the elevator. Once I left, they did an unbalanced forces lab practical in Pivot Interactives.

Days 64-67: Kinetic Energy & Newton’s 2nd Law

This week was a little goofy. Tuesday was our first day back from break, then a big winter storm meant we had to close schools on Wednesday. We used up our regular snowdays in December, so Wednesday was an emergency e-learning day, which means students completed asynchronous assignments.

AP Physics 1: Kinetic Energy

Our first task back from break was to find the relationship between velocity and kinetic energy. I waffle every year whether to do this with tracks and probeware, which as the advantage of being firmly rooted in the real world for students, or use Pivot Interactives, which has the advantage of measurements that are easier to make. With the weather forecast, I opted for Pivot. I had students complete the first section that takes them through making measurements and modeling the energy transfers with energy bar charts individually, then complete the remaining sections in groups. It’s been a little while since we linearized a graph or developed a mathematical model from data, but I was really pleased with how they did.

Physics: Newton’s 2nd Law

Our big goal this week as a paradigm lab for Newton’s 2nd Law. In some conversations last year, Kelly O’Shea suggested using carts on ramps as an alternative to the more standard modified Atwoods machine. Students used a force sensor to measure how much force it took to hold the cart in place. Next, we used some vector addition diagrams to reason out the force they’d measured is the same as the net force when the cart is released. Students used the motion encoder carts to determine the acceleration, then changed the angle of the ramp and repeated their measurements. I really like that this is conceptually much simpler than the modified Atwood, so students can focus on making sense of the data, and this approach makes a really clear conceptual link between balanced forces and unbalanced forces. For the e-learning day, we had students do some reasoning with vector addition diagrams of balanced forces to help review those skills to support the lab.

Days 61-63: Energy Bar Charts & Newton’s 2nd Law

This was supposed to be a four-day week, but an impending winter storm means we will be starting our winter break a day early.

AP Physics 1: Energy Bar Charts

This week I introduced students to energy bar charts and we spent a lot of time working and whiteboarding problems. Since we had two rounds of whiteboarding in a 3-day week, I asked students if they wanted to change it up from mistakes whiteboarding, but they were adamant that mistakes whiteboarding helps them learn. I was more concerned about whether they would be up for engaging in that much mistakes whiteboarding than whether it would be useful, so happily went along. I am really glad that they are seeing the value in making, analyzing, and discussing mistakes for their learning. I also had some great conversations with students this week where they talked about the growth they feel like they are making in this class, which is fantastic. That is a great note to go into winter break on.

Physics: Newton’s 2nd Law

This week felt more awkward with this course. We had a quiz on Monday that had been pushed from last week due to a snow day. Then the plan was to start the lab we’ll be doing on Newton’s 2nd Law. We are planning to use the motion encoder tracks, but students haven’t had any hands-on experience with them yet and haven’t used any velocity vs. time graphs in a few weeks. To address those issues, I put together an activity where students reviewed position vs. time and velocity vs. time graphs using the motion encoder tracks. That seemed to really help students feel comfortable with the equipment and set up what they’ll need to remember to find acceleration in the lab. That left us with today to start the lab. I dragged my feet on the introductory discussion rather than starting data collection, then picking it back up after two weeks off. We’ll see what I think of that decision when we come back from break!

Days 57-60: Impulse & Force Practicals

We had a snow day on Thursday, so got a surprise short week. Plus some beautiful fresh snow to enjoy this weekend!

AP Physics 1: Impulse

This week, we wrapped up impulse. I tried a new sequence this year where I started with conservation of momentum, then shifted into impulse and using momentum for single objects. I feel like my approach could still use some refinement, but overall I felt like the storyline made a lot of sense. My students found it a little tricky this week when we did some problems where they had to switch between different systems when thinking about the same scenario, which tells me that’s something I need to make sure we keep working on. We are starting energy next, which is a good opportunity to keep working on the idea of systems.

Physics: Force Practicals

This week we did a lot of work doing problems with balanced forces. Students were in a lot of different places on their math skills, but were able to get the problems down. We finished the week with two different lab practicals. For one, students had to find the mass of a cart on an angled ramp. For the other, students had to find the mass of a bag hanging from two spring scales. I set up several stations for this lab practical on my whiteboard using hooked magnets, and I was excited to see some students sketch diagrams on the whiteboard right by their station. On both practicals, I was really pleased by how quick students were to check their answers on the scale I had out. Last year, it was really tough to get students to see the connection between the physical world and the math we were doing, and one way that showed up is a lot of students were not invested in checking their answers on lab practicals. I think sketching diagrams on the whiteboard next to the practical also helped cement the links between the representations we’ve been using and the physical scenario.

Days 53-56: Impulse & Vector Addition Diagrams

After a staff development day on Monday, we started trimester 2 this week. This trimester, I’m adding two sections of Physics to my teaching load.

AP Physics 1: Impulse

This week we spent a lot of time working with impulse. Near the end of last trimester, it clicked for me that my students have been very quick to grasp conceptual thinking and can do great on problems like those from TIPERs, but need more practice than I’ve been giving them on calculations. To help with that, we did a lot of whiteboarding calculations this week and did a lot of work making sure everyone grasped the connections between momentum bar charts, force vs. time graphs, and the equations we’re working with. This was the kind of week where I really saw the value of frequently changing groups; since students were with different people almost every day, they were pushed to do a lot of explaining their thinking to each other rather than falling into the shorthand that can happen when you are working with the same people consistently.

Physics: Vector Addition Diagrams
This week, we did a lot of work translating between free body diagrams and vector addition diagrams. We did an activity I love from Casey Rutherford where students make arrows out of pipe cleaners over the FBD, then rearrange them to make the VAD. Students had done some practice with this at the end of last trimester, so things went pretty smoothly, but it was helpful for me to start getting a feel for what they have down and what they need more work on before we start adding in calculations.

One thing that felt a little tricky this week has been figuring out how to establish the classroom culture that I want. Usually, around half of our students stay in the same hour for physics when a new trimester starts, so I’ve gotten used to have to do some culture-building at the start of a trimester for the students who are new to the hour, especially if they had the other physics teacher, but I have a foundation to build on thanks to the students who’ve been in that hour since September. What’s been tricky this week is there is still a core of students who have been with each other in this space doing physics together since September, but they were with a different teacher who has some differences in the kind of culture he builds, so I’m asking students to unlearn some things that have been established as part of physics class for the majority. I’m trying to be really explicit about why I’m doing things the way I am and leaning much harder into culture-building strategies than I normally do at this point in the year, but I think we’ll get here.

Days 48-52: Model Summaries & Final Exam

We are on trimesters, so this week was the end of tri 1. We usually have a special schedule for final exams the last two days of the trimester, but, due to bussing issues, we followed our normal schedule. We also had a change in our grading policy to do away with cumulative final exams.

I still opted to give a modified practice AP exam covering what we’ve done in class so far. I usually spend 45 min on each half of the exam, so that made it easy to split the exam over two days with our standard 55 min periods. To meet the modified grading policy, I gave my students some points in the formative category of our gradebook for completing the practice exam. This is more in line with how I use the first practice exam, anyway. At this point, I mostly care about students seeing what a test is like and trying their endurance on something longer than our usual quizzes. I also use it to get a sense of what my students are doing well so far and what I need to make sure we keep working on. Even though their grades would not be impacted by how they did, my students took the practice exam seriously and I’m very pleased with how they did.

The practice exam is a good opportunity to review what we’ve done so far, and my favorite approach is model summaries. I gave each group a model that we’ve used so far this year, and asked them to put a scenario on their whiteboard where they could apply their model. Then, I had students add as many diagrams and representations of their scenario as they could. I explained this exercise to students as each model is a toolbox, and we were going to use these whiteboards to remind ourselves what tools come in each box. There were at least two groups whiteboarding each model, which worked out nicely since it’s pretty common that different groups will make use of different tools from the model, so we get a more complete summary with two groups.

Now on to trimester 2! Due to ongoing staffing issues, I’ll be adding two sections of regular physics to my current teaching load of one section of AP. I think a major theme of the next few weeks for me will be figuring out how to balance additional teaching with my responsibilities as a content specialist.

Days 46-47: Conservation of Momentum

We made it to Thanksgiving break!

This week we wrapped up conservation of momentum. I’ve been liking doing this before impulse since collisions give us a clear reason to make use of conservation of momentum, but I ended up introducing momentum by just giving students the formula and telling them to calculate it for a bunch of collisions, which worked, but I wasn’t thrilled with. I want to keep thinking about how I could better introduce momentum with this sequence (though in theory I won’t be teaching next year…).

On Monday, I had students work through an activity I’m working on for Pivot Interactives where they switch between thinking in terms of two exploding gliders as a single system and thinking of the gliders as separate systems. I was really pleased with how my students did switching between those two types of thinking after the limited intro to impulse we’ve had. I am wishing we’d spent a bit more time on calculations with momentum before our quiz this week. I usually give students two in-class assessments over every learning target, so I’ll have to make sure we get some more practice before our retake.

Days 41-45: Conservation of Momentum & Newton’s 3rd Law

This week we developed conservation of momentum. Previously, I started with impulse and momentum of single objects, then built up to conservation in systems. I’ve never been thrilled with my storyline, so this year I am trying putting conservation of momentum first, then we will work toward impulse. Once we’d done a lab with some collisions and talked about momentum bar charts, we did Kelly O’Shea’s multiple representations of momentum card sort to incorporate mathematical representations. The card sort really helped my students feel confident with the bar charts and to make sense of the mathematical representations.

We ended the week with Newton’s 3rd Law. I feel like this law fits better with my momentum storyline than my forces one, so this was their first introduction to the 3rd Law. I had students predict how the forces would compare on two carts for a variety of collisions, then we actually tested the collisions out using some force sensors with hoop springs. This is a very rare time that I ask students to make a prediction that I think they are likely to have wrong, so was very intentional in talking to students about my goal of pulling out their existing ideas so we could contrast with the accepted physics. I also made sure we talked about what useful thinking lead them to the incorrect predictions and what physics their predictions showed they know. There was a fantastic moment partway through where a student articulated that both the forces we were measuring came from the same interaction, so it made sense for the size of the force to be the same. She also realized the cart she expected to experience a bigger force did have a bigger change in motion, which was a great opportunity to validate the thinking that lead to that prediction. It was a great note to end the week on.