Days 142-146: Projectile Video Analysis & Angular Momentum

Physics: Projectile Video Analysis

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.

Days 110-112: Energy Pie Charts & Pendulum Practical

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.

Days 100-104: Momentum Conservation & Projectile Practical

Physics: Momentum Conservation

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.

Days 95-99: Cart Explosion Lab & Projectile Graphs

Physics: Cart Explosion Lab

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.

Days 90-94: Impulse Problems & Energy Practical

This week we were back in-person after two weeks online.

Physics: Impulse Problems

A big theme I saw across my classes is that students had a pretty decent grasp of impulse, but didn’t think they had learned much the last two weeks. I kept thinking about my PhD research so far where, in some data I collected pre-pandemic, I found that even when students were mastering the material, they struggled to build confidence and self-efficacy from activities that were purely computer-based. In addition, right before we went online, my students also made clear that they really value discussion and collaboration as a way to learn physics, but I struggled to get students talking to each other online. With those things in mind, this week was all about giving students space and time for discussion and collaboration to build their confidence. We spent a lot of time whiteboarding various problems, including some that were assigned while we were online, so that students could talk to each other. I also gave much more feedback than usual while students were working on whiteboards to point out what they had correct or what they were doing well, which seemed to really help students see just how much they had learned the past two weeks.

AP Physics: Energy Practical

My students have been feeling pretty good about doing problems with conservation of energy, I think in part because we were able to start them in-person, then do a lot of practice while we were online. I wanted to give students something hands-on before we wrap up energy, so I got out the popper hopper toys and tasked students with finding the spring constant. To help my students with writing procedures, I had each group write a procedure on a whiteboard, then give it to another group to follow. They were allowed to go ask the group who’d written the procedure questions to clarify steps or discuss changes as both as a way to give feedback to the group who wrote the procedure and to ensure that every group was able to complete the task, even if there were issues with the procedure they were given. I think that helped give students a concrete target for what needs to be in a procedure.

Days 85-89: Impulse & Energy Problems

This was our second week of virtual instruction. We are slated to be back in person on Monday.

Physics: Impulse Problems

Students worked on problems using the impulse-momentum theorem. I noticed that a lot of students were struggling to retain new information much more than usual, which made the problems relatively challenging. I’m sure some of it is a lot of students are less focused right now than in the classroom (at least some of them for very good reasons, like helping take care of younger siblings that are also at home), but I it’s also a factor that I didn’t make much effort to encourage student-to-student discussion and I did more providing new information than usual, rather than simply stepping in to put language or standard formulas to things students had already said. I’m not beating myself up for it since those things are difficult online in the best of circumstances, and I was doing it with minimal time to prepare and no prior experience teaching high school online. But it is a good reminder that the time I spend on those things in the classroom is important. While we have done versions of everything we normally do before the impulse quiz, I’ll be taking a few days next week to have some in-person discussions before we assess for the first time.

AP Physics: Conservation of Energy Problems

Right before my school switched to remote instruction, my students started working some problems using conservation of energy. We didn’t get a chance to whiteboard or discuss the problems, so we revisited them this week. My students had some good conversation using Jamboards and a discussion forum and seem to be doing pretty well with conservation of energy problems. I still want to do some in-person whiteboarding before we assess to get a better sense of where students are at since there are a few who’ve shared they are having some of the same trouble focusing I saw in Physics. I’ve got some problems from the AP Physics 1 workbook that I think will be good for this purpose.

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 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 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 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.