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!
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.
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.
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.
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.
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.
Students used Vernier Video Analysis to get velocity vs. time and position vs. time graphs for a projectile. I saw some students including their throw or after the projectile landed in their video analysis, which makes sense since I’ve seen students struggling more than in the past with recognizing what is the most relevant part of an object’s motion. I think that probably could have been addressed with spending a little more time on some pre-lab discussion. It was a lot of fun to hear their small-group discussions making sense of the graphs once I had them draw a free-body diagram and they recognized why the graphs looked the way they did.
AP Physics 1: Angular Momentum We wrapped up unbalanced torque and rushed through angular momentum. Students started an activity in Pivot Interactives, but were moving through it more slowly than I’d hoped, so I ended up doing a lecture on angular momentum. It’s not my preferred approach, but the clock is ticking for AP exam day! Students seemed to get the concept during the lecture. I did a lot of emphasizing the parallels to linear momentum, which seemed to help. We’ll be doing some problems and whiteboarding next week to wrap up angular momentum, which will be a good opportunity for me to check how clear their understanding is.
With President’s Day on Monday and a PD day on Friday, we had a 3-day week.
Physics:Energy Pie Charts
This week we did mistakes whiteboarding with energy pie charts. There was some great discussion, both as students prepared and as they presented the whiteboards, that came from students working through what differences represented someone making a mistake vs. what differences represented different, but equally valid choices.
We also briefly revisited momentum transfer this week. On the last quiz, I saw a lot of evidence that students were struggling to connect the equations and math for conservation of momentum to their momentum bar charts, which fits with a larger pattern I’ve seen this year of students struggling to connect different representations. As we get into conservation of energy at the start of next tri, I need to give a lot of thought into how I’m going to support students in making connections between mathematical and graphical representations. I do a lot of card sorts to try and help with these connections, but I think I might need to plan some discussion that specifically focuses on how the mathematical representations relate to the diagrams.
AP Physics: Pendulum Practical
This week, we wrapped up pendulums. My students could use more practice and feedback on designing experiments and writing procedures, so I decided a pendulum practical would be a good opportunity to practice this. I tasked students with finding the length of a string without using a meterstick or ruler. Before they could get their string, they had to write out their procedure on a whiteboard and get it approved by me. I think this would have been tough to manage in a large class, but I currently only have 11 students in AP, so was able to pretty easily take time to give groups meaningful feedback and check their revisions before cutting them a piece of string to use.
This week we did a lot of work on conservation of momentum. We started with using photogates to measure the velocity of carts before and after a collision to reinforce the idea that momentum is transferred, then we did a momentum representations card sort from Kelly O’Shea before students tried some problems on their own. One thing I noticed is a lot of students are still struggling with what momentum is. I think a lot of students were having trouble taking in new ideas during distance learning, and are now struggling to build on those ideas. Students had a lot of great conversations during the card sort, and it was a lot of fun to see how they applied that thinking to the problems later in the week.
AP Physics 1: Projectile Practical
This week we wrapped up projectile motion. Students did a projectile practical where they predicted where a marble would hit the floor. I like to take advantage of the different masses of marbles I have and ask students to predict how the landing spot would change if they switched to a lighter marble, and students consistently nailed it. One fun thing has been seeing students use multiple different models to think about projectiles and the confidence I’m starting to see from more students.
This week, we wrapped up the cart explosion lab and started working on momentum bar charts. My students had really good results on the cart explosion lab, but connecting it to momentum in the discussion is always rough. Students launch a spring-loaded cart and a standard cart off each other, figuring out where on a track to start them so they reach the ends at the same time, then record the ratio of the cart’s masses and the ratio of the distances they travelled before changing the mass and trying again. While I love that this low-tech approach incentivizes students to look for a pattern while they are collecting data, students struggle to connect the distances travelled to the velocities, I think mostly because there are so many different numbers flying around. During the discussion, my students had great results, but needed a lot of support to connect them to momentum. I want to rethink our momentum unit anyway, and I think part of that will include clarifying what I want students to get out of this lab and whether there are better ways to achieve that purpose.
AP Physics 1: Projectile Graphs
We started the week with a Pivot Interactives activity that shows three views of a projectile (full disclosure: I am an activity writer for Pivot Interactives). I’ve done video analysis, but I really like the way seeing the motion from different angles solidifies what I mean by the horizontal and vertical motion. It’s been a while since we did much with velocity vs. time graphs and students made solid connections to the forces acting on the projectile. We also worked through an activity I got from Michael Lerner where students describe the motion of an orange falling from a tower using every model we’ve learned so far, which really helped reinforce for students are aren’t really doing something new, just applying what we know to a new context.