# Days 92-96: Springs & Impulse

On Friday last week, I found out our new physics teacher would be starting this week. I went into this year expecting to be doing my role as science content specialist full-time and it has been tricky to juggle that work with my teaching. I’m excited to be able to focus more on my role, but it is hard to be getting ready to leave students I’ve been with for a while. The new teacher shadowed me this week so he could start getting to know the students and the curriculum. We will then be co-teaching until the trimester ends on March 10. Trimester 3, he will take over Physics completely. I’ll still be in AP Physics 1 on occasion up through the AP exam since this is our new teacher’s first time doing AP and it’s a lot to get the hang of in a short amount of time!

AP Physics: Springs

Students conducted an experiment to find factors that affect the period of a spring. The data was kind of rough, mostly because they were having trouble getting the springs to oscillate nicely. We still had enough good data in the class that we were able to figure out all the things we needed to. On both this and the pendulum lab, I was really pleased with how students used the intercept of their graph to figure out they needed to linearize. After the lab, we worked on some problems with representations for simple harmonic motion. It was a lot of fun to see students putting together forces, energy, and motion graphs to make sense of simple harmonic motion and they made a lot of great connections.

Physics: Impulse

This year, we tried a new sequence for momentum where we started with conservation of momentum since looking at a system that includes both objects in a collision is a really strong motivator to learn momentum. This week, we did Newton’s 3rd Law and used that combined with Newton’s 2nd Law to derive impulse and start thinking about individual objects. This was a tough transition for a lot of students to make and I’m wondering about ways we could make it smoother in the future. One thought is we don’t emphasize system choice in Physics, but that is pretty key to thinking about impulse. I’m not sure what to do with this thought yet, but definetly want to keep it in mind.

# Days 87-91: Pendulums & Conservation of Momentum

AP Physics: Pendulums

This week we started simple harmonic motion. We started by using a video on Pivot Interactives that has a pendulum, a glider on a spring, and a spinning disk that all go through simple harmonic motion with identical periods and amplitudes. Students plotted position vs. time and velocity vs. time graphs. When we shared the results, the students in calculus made some great connections to derivatives. We then moved into a lab to find the factors that affect the period of a pendulum. This is one of the labs where I felt like the hard work learning how to do an experiment really paid off as students worked pretty independently and got great results.

Physics: Conservation of Momentum

This week students worked on practicing conservation of momentum problems. One of their tasks was to figure out an unknown mass using results from a collision. One thing that has been tricky every time we do this practical is students sketch bar charts for what they want the collision will be, such as having both carts come to rest after a collision, but have trouble adjusting if their bar charts don’t match the actual collision. I think this comes down to many aren’t thinking of momentum bar charts as something that describe a physical event. I wonder if it would be helpful to do an activity where students do various collisions between pairs of carts, but focus only on representing those collisions with bar charts.

# Days 82-86: Projectile Calculations & Momentum Conservation

AP Physics: Projectile Calculations

This week we worked on wrapping up projectile motion by focusing on calculations. Students were a little rusty on using velocity vs. time graphs to set up equations since we haven’t practiced it in a while, but I was very pleased with how quickly they got back into the groove with those skills. We ended the week with the classic projectile practical where students predict how far from the table a marble will land and it was great to not only see students nail it, but feel good about nailing it. Once students succeeded, I gave them a lighter marble and asked them to predict where it would land relative to their original, heavy marble, which lead to some great conversation.

Physics: Momentum Conservation

This week we started transitioning to quantitative momentum conservation, including a lab where students did a series of collisions and comparing the total momentum before and after the collision. It’s always tricky for students to make sense of the graphs produced by the photogates, so this year when we had some extra time the day before, I tried doing a few collisions and projecting the results. Then, I had students get into groups and whiteboard their interpretation of which velocity was which. That exercise paid off and the lab went the smoothest it ever has for me as students were much more confident at reading the graphs with the skill to back it up! We ended the week with Kelly O’Shea’s momentum card sort, and there was a really great moment where a student was explaining to me how he worked backwards to make a velocity vs. time graph from an equation by solving for the unknown velocity. Given how much I see students struggling with math reasoning, it was a lot of fun to see a student feeling confident enough to make sense of the equation in that way, which I don’t think would have happened if we’d gone straight to problems.

# 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 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 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.

# Days 37-40: Unbalanced Forces

This week was a little funny because we had Tuesday off for elections.

On Monday, I gave a quiz over unbalanced forces that didn’t go as well as I’d hoped. The big thing students seemed to struggle with was sketching and using free-body diagrams and vector addition diagrams. I decided to put off starting momentum to spend a little extra time working on force diagrams. We started with a card sort with unbalanced force diagrams. Including the motion maps gave me a chance to emphasize the net force is in the same direction as the acceleration, which I hadn’t done a great job of before. This card sort also includes two sets of similar scenarios, which lead to some good conversation comparing and contrasting the similar scenarios. After the card sort, one student told me that she has found card sorts in general to be a really useful tool in helping to visualize what diagrams should look like. I realized one of the benefits of card sorts is they students the visual they are after when they ask me to do example problems on the board, but kept the bulk of the sensemaking on students. We have a lot of card sorts made for our physics courses, but I don’t use them consistently in AP in an effort to keep to a fast-moving pace. This week was a good reminder that it is worth it to make time for card sorts.

After the card sort, we moved into doing some problems, both calculations and conceptual, and students were much more confident and doing much better than earlier in the week.