# Days 20-23: Mathematical Force Models

This was a short week due to a PD day on Friday.

This week, we focused on building mathematical models for the force of gravity and spring force. My students have taken very nicely to writing equations for lines of best fit in “physics” where they add units to their slope and intercepts as well as use variables that match their experiment. My students are also taking nicely to using “for every” statements like “the force goes up 10 N for every 1 kg of mass” to think conceptually about the meaning of their slopes. Students have also done really well with turning their intercept into statements like “the intercept is the size of the force when the mass is 0 kg” to think about what kind of intercept makes sense.

With the spring force experiment, I had students stretch their springs both vertically and horizontally to see the graph had the same slope in both directions. This usually seems to help address conceptions about the role of gravity in the behavior springs that come up when we get to energy and simple harmonic motion.

# Days 1-4: Buggy Lab

I’d expected to give this blog a break for this year, but a last-minute resignation meant I’m back in the classroom for at least part of this year. At the moment, I’m just teaching one section of AP Physics 1.

Like usual, I started with the buggy lab. Like I’ve been doing for a few years, on day 1, I asked students to make a graph that models the motion of their buggy with almost no other instruction, then had a board meeting that focused on what we would need to change in order to set ourselves up better to compare results across groups. Then, the next day, we repeated the lab with some agreements about things like units and graph axes so we could compare results. Every group collected one set of data with a full-speed buggy moving forward from zero and one set of data with a variation I assigned them. In the board meeting, students easily recognized the slope represented he speed and the intercept represented the starting position.

In the past, I’ve insisted students use time as the independent variable and collect data at even time intervals, but I skipped that this year. I ended up regretting it because the ways students measure when time is the independent variable lead so nicely into a motion map, so that could make next week trickier since only a few students have had that experience.

# Days 157-161: Pendulums & AP Review

Physics: Pendulums

We spent most of the week on the pendulum lab exploring the variables that affect the period of a pendulum. This will be our last model-building lab for the year, so it was good to see students figuring out plans for data collection and getting high-quality data with minimal intervention from me. Connecting the data to a mathematical model was still tricky for students, but they worked through the challenging parts to figure out what was going on. They really hated the unit on the slope of their period vs. square root of length graph (I don’t blame them!), but I was able to use that as motivation to try and get a nicer unit by rearranging things so that we had the length divided by a number in m/s2. From there, students were quick to suggest that the slope has something to do with gravity. From there, I showed that the value happened to work out if we put a 2π out front. This approach could use some refining, and I’d especially like to put more of the thinking on students, but students did seem clearer on the significance of the slopes of their lines than in the past.

AP Physics 1: Review

With the AP exam on Thursday, the first three days of this week we focused on review. My students this year really liked Plickers for multiple choice and had some great discussions, when whole class discussions have generally be tough this year. I wonder if I should have pulled out Plickers earlier in the year as a way to get them talking and to build up to some other types of class discussions.

I had a brainstorm for a review activity, that unfortunately came the day of the AP exam, so too late to try. I do a lot of having students start by just looking at the diagram and scenario description, then deciding what models seem useful and sketching some diagrams. It crossed my mind this could lend itself to a card sort, so I put one together with the released free response to date. I haven’t tried it with students, but I think I would start by having students match each prompt to at least one of our models, then give each group a problem to sketch some diagrams and brainstorm what they could figure out.

# 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 1-5: Tumble Buggies

After a year away, I am back in the classroom this year, teaching Physics and AP Physics 1. This past week was our first week back. Between having been away for a year and the continuing dangers of COVID-19, I have been very nervous about going back to the classroom, but this week reminded me why I decided to come back. It felt so good to be in a classroom with a bunch of teenagers doing physics together.

This year, I convinced the other physics teacher we should skip a short “intro to physics” unit and we dove straight in to the buggy lab, so both my courses looked pretty similar. On the first day, students were just given the vague direction to make some kind of graph or chart on a whiteboard that modeled the motion of the buggy, then we talked about what was making it easy or hard to compare results across groups. Throughout the activity, I emphasized that the choices students made were correct and valid in the context of the activity, but I needed to do more as a facilitator to prepare them to compare across groups.

We then did a second round of buggy data collection with more structure. I also had students do a linear regression for their data and “translate” the resulting equation into physics by adding units and substituting variables that matched their experiment. Interestingly, for all of the rhetoric about learning loss and concern about the gaps students will have this year, this is the smoothest the “translation” has ever gone for me. Even better, my students were thinking about what their regression line actually meant without any prompting from me. I had several groups call me over concerned because they had already figured out on their own that their intercept should match their buggy’s starting position, but the two values were different by 5-10 cm, which meant I got to have some great conversations about uncertainty much earlier than usual. I also had a student who was struggling with adding units to her slope. As I was asking her questions to try to better understand what she was having trouble with, her face suddenly changed and she said “Oh! The units mean the slope is how many centimeters the buggy travels every second!” and I realized she wasn’t struggling with the mechanics of placing the unit in her equation, she was struggling because she knew a number with a unit needs to mean something, which is a fantastic reason to be struggling.

My classes have been quieter and more still than usual, even in the first week, but I’m guessing they are also feeling nervous and overwhelmed about being in a full classroom again. But given the sensemaking they are doing without any direct pushes from me, I think my classes this year are going to be pretty great as long as we all stay healthy.

# Distance Learning Week 8

We’re nearing the end of the school year. Seniors finish on May 29, and we’ve been asked to finish instruction by today so that next week can be reserved for students to work on missing work and reassessments.

AP Physics 1: Wrap-Up

Rather than start anything significant after the AP exam, I decided to keep this week fairly easy. I asked students to fill out an end-of-course survey and posted a discussion board where they can share how their family is celebrating graduation. Based on the responses so far, the most useful questions I put on the survey are about what other teachers did during distance learning that helped students learn and helped them feel connected to their class. I’ve had very few conversations about teaching with other staff in my building during distance learning, so it’s been very helpful to hear what’s happening in other classes and identify some teachers who’s brains I need to pick. Assuming we have some distance learning next year, I want to ask my building leadership to figure out ways for teachers to do a better job of sharing with each other.

Physics: Spring Period Calculations

Students finished up a lab to figure out what affects the period of a spring. It was a little frustrating that, just like in the period vs. length graphs on pendulum lab, most students described their period vs. mass graphs as linear, even after recognizing the intercept should be zero. While I was frustrating, it isn’t surprising that students struggled here. When we’re face-to-face, most students usually describe their graph as linear, too, until someone brings up the intercept during the board meeting. I think there are two main issues leading to this.

First, even though we have a question on our standard lab packet about whether the intercept makes sense, we haven’t done a great job of helping students connect the expected intercept to the shape of the graph. As a result, students treat questions about the intercept as completely separate from questions about the shape. Face-to-face, even if kids aren’t ready to make that connection independently, the conversation during the board meeting gets everyone there. I think I could make better use of discussion boards to get something similar in an online environment.

Second, we don’t talk much about uncertainty in this course, so students have trouble deciding whether an intercept is big enough to matter. At the start of the year, I see students giving a lot of weight to very small intercepts and, by the end of the year, I see the opposite with students quick to say fairly large intercepts are effectively zero. I think it would help if we incorporated some very basic uncertainty next year. One option may be to have students estimate how far they may be off on measurements on the vertical axis, then compare that to the intercept they get.

Chemistry Essentials: Balancing Practice

Students continued working on balancing chemical reactions by doing another set of practice problems, this time including some formulas with polyatomic ions. I haven’t heard from any kids with questions this week, so I assume it’s going smoothly. I’m focusing a lot of my time on students who haven’t been engaging in the course, and have gotten a few of the kids who weren’t on track to get a credit to turn some things in. Today is the last round of parent phone calls, so hopefully I can help a few more kids get on track to at least pass the class.

# Days 89-92: Waves & Momentum Practical

We had a four-day student week for a professional development day on Friday.

AP Physics 1: Waves

This week week we worked on developing and using the wave equation, as well as a few other concepts on mechanical waves. We started with a standing wave lab in Pivot Interactives. On a few labs this year, students haven’t taken the time to get good quality data, which has made it tough to make sense of the slopes during the board meeting. As students are getting better at constructing new ideas from lab results, they are starting to really see the value in having good results to discuss and this lab was a place I saw it really pay off. Students worked through linearizing their graphs and figuring out units of their slope with very little intervention from me partly because they knew those steps would help their sense-making and partly because they are getting more skilled and need less support. Every group had beautiful data for the board meeting and, as we worked on problems later in the week, I heard a lot of students referring back to their graphs or their qualitative observations to think through a problem. All around, this was a really fun week to watch and listen to my students.

Physics: Momentum Transfer Practical

Students worked on applying conservation of momentum to problems, including a lab practical. For the practical, students had to determine an unknown mass using photogates and a dynamics track. The groups that were able to sketch momentum bar charts that matched the collision they decided to do were typically able to find their mass pretty quickly, but a lot of students struggled to connect their bar charts to what was happening on their lab table. As we move into energy, I need to think about how I’m going to make sure students are connecting representations like bar charts to things they can observe or interact with in the lab and beyond. I did enjoy seeing the different approaches groups took to the practical. One based their approach on cart explosion lab and added mass to their empty cart until both carts had the same velocity after the explosion.

# Day 36-40: Newton’s Laws & Whiteboarding

AP Physics 1: Newton’s 2nd Law

Students used a modified half-atwoods to find a relationship between force and acceleration. The quality of the results varied a lot. I’ve been talking to the AP Chemistry teacher, and we think part of what’s going on is students aren’t often asked to use their data in meaningful ways before they get to physics, so it doesn’t make sense to take the time and attention to collect data carefully. I need to put some thought into how to help students place value on good data collection and build the skills required to collect good data.

After developing Newton’s 2nd Law, we spent some time combining the new equation with vector addition diagrams. Students are starting to buy in to the diagrams as useful thinking tools, which is always a lot of fun to see.

Physics: Free-Body Diagrams

Students have been working on Newton’s 1st Law and drawing free-body diagrams. We have some problems that often lead to great discussion with mistakes whiteboarding, but I’ve been struggling to get students in one of my hours to speak up during whole-class discussions. To help with that, I tried doing a short gallery walk prior to any of the whiteboard presentations this week. Once the whiteboards were ready, I had students visit each board with their group and make notes on their worksheet about potential mistakes they saw or questions they had. During the whole-class discussion, there was a lot less silence and we heard from some students who don’t often speak up, which was exactly what I was hoping for. I think it also helped that I shared those goals with students before we started. When a student joked those goals aren’t going to happen, I assured her I’m very stubborn and am convinced the class can get there.

# Days 20-23: Newton’s 1st LAw & Constant Acceleration Model Building

This week was a little goofy. Students were off Friday for a staff development day and it was homecoming week, so classes were shortened on Monday and Thursday for festivities.

AP Physics 1: Free-Body Diagrams

This week was all about Newton’s 1st law. We started with the bowling ball lab to come up with a formulation of N1L, then worked on representing forces with free-body diagrams and system schema. Both sections had mistakes whiteboarding sessions that were overall really good. There was a debate about whether a projectile should experience air resistance that had a lot of good thinking. We ended up grabbing a softball out of the storeroom and capturing an image of it rolling in Motion Shot to see if it had a constant velocity. There was a much more intense debate about air resistance than I’ve seen before and I think the group presenting felt like it became a “gotcha” moment. I need to think about how I could have intervened differently in that discussion to shift the tone it took on.

Physics: Constant Acceleration Model Building

Students used video analysis to produce graphs of the motion for an object on a ramp. I was ornery about making students attempt to follow a reference guide I made before I’d help with the technology, which made it a lot easier for me to spend time with students who needed help troubleshooting. The results were better than when I’ve used photogates, but still fairly messy. I think part of the problem is, regardless of the approach, students rush on key pieces and get sloppy data as a result. I need to think about how to slow my students down at key steps. It was also tough to get students to speak up during the board meeting, even with doing a gallery walk and jotting down some observations with their group beforehand. I’ve got more students than usual who underestimate how much they know and are wary of jumping in as a result. I have some work to do on increasing the social safety in my classroom and helping students recognize their contributions.

Students also did Kelly O’Shea’s CAPM card sort. Interestingly, even though this fell on the day of our homecoming pep fest, students were overall very engaged in the activity. I saw a lot of the same students I struggled to get to speak up during the board meeting asking great questions and sharing ideas during the card sort. I think the small group setting was a factor. I need to give some thought to what else made students comfortable speaking up so much in their small groups and how I can bring that to whole class discussions.

# Days 5-9: Board Meetings & Problems

This week’s big theme was using precise, specific language in physics.

Physics: Buggy Lab & Problems

Students did the buggy lab, then worked on some problems with constant velocity representations. We went over the problems using Kelly O’Shea’s mistakes whiteboarding. Both during the buggy board meeting and during the mistakes whiteboarding, students used a lot of phrasing like “the slope is increasing” to indicate a positive slope or even just saying “the buggy was decreasing”, rather than specifying what about the buggy is decreasing, which made for some good opportunities to pick apart that wording and try to find ways to make it clearer what they meant. A few students seemed like they were frustrated by these conversations, especially during mistakes whiteboarding when a group didn’t consider that one of their mistakes, which tells me I need to keep working on emphasizing growth.

AP Physics 1: Problems & Acceleration Model-Building

AP also had their first round of mistakes whiteboarding this week. While we had some similar conversations about language, I noticed fewer students who seemed frustrated by those conversations. I don’t think I approached getting nitpicky about wording differently than I did in Physics, so I’m not sure if the AP students were doing more hiding their frustration or if they are bringing something to the class that leaves them less bothered by me getting picky about language.

After the problems, we started a model-building lab for constant acceleration where we used photogates to produce a position vs. time graph for a cart on a ramp. This lab is fairly teacher-directed since its the first time students are using any LabQuest probes, and it takes a while to get through. I’ve thought about switching to motion detectors or video analysis, but with the limited computer access I usually have, I like that photogates produce data that students can linearize. My building added a lot more laptop carts this year, so I might try one of the other options when Physics gets to acceleration.