Days 63-67: LOL Diagrams & Newton's 3rd Law

AP Physics 1: LOL Diagrams

Students worked on sketching bar charts and LOL diagrams to show energy transfers. I was really pleased with how comfortable students were switching between different systems. I started out the week by having students use a spring scale to pull a cart up different ramps, always raising their cart to the same height above the table. We then sketched force vs. displacement graphs to introduce the idea of work and gravitational potential energy. Getting both simultaneously meant the concepts blurred together for students at first, but that issue got resolved as we did mistakes whiteboarding with energy bar charts and LOL diagrams.

Physics: Newton’s 3rd Law

One of our major tasks this week was developing Newton’s 3rd Law. Students started by predicting how the forces on two colliding carts would compare, then we tested out the collisions. As we tested the collisions, I cued students to notice the relative accelerations of the carts, which I think helped students see the useful thinking in their original predictions. Before we officially stated Newton’s 3rd Law, I borrowed an idea from Mark Schober and had students play with film canisters with magnets inside to test and refine their rule before the whole-class discussion.

Days 58-62: Card Sort & Momentum Bar Charts

This post has ended up a few days late. But I still have yet to miss an intended post on this blog!

Physics: Unbalanced Forces

Students did the classic Newton’s 2nd Law lab with a half-Atwoods machine, then we started fitting net force with the diagrams we’ve been working on. The first set of problems we typically do is just sketching diagrams. This year, we decided to try turning it into a card sort, which I think really helped students who were new to me transfer their knowledge of force diagrams into my classroom, something I’d been thinking about leading into the term. I also pushed using motion maps with acceleration arrows much harder than I have in the past, and one of the results was I got almost no questions this week about which direction the net force should be in.

A set of cards with descriptions of a scenario, free body diagrams, vector addition diagrams, and motion maps

AP Physics 1: Conservation of Momentum

We wrapped up the momentum transfer model (at least for now) by working on conservation of momentum. Students were very excited about Michael Lerner’s watermelon on wheels problem. Aside from being silly, I really like that it pushes students to play with viewing a single scenario with multiple different perspectives. We also did a little bit with momentum bar charts, since they show up in the AP Physics 1 workbook we did a few problems out of, and I found they really helped a lot of my students. I need to make much more use of those bar carts next year.

Days 56 & 57: Finals & Reflecting on Tri 1

This week, we had finals on Monday and Tuesday. Wednesday was scheduled as a professional development day, but an early blizzard meant we had a remote work day for term transition, instead.

AP Physics 1

For the final exam, I had students take a modified practice AP exam. As usual, students did much better on the free response than the multiple choice. I need to give some thought to what shifts might address that. I’m also giving some thought to shifting how I use the formula sheet. Typically, hand out copies of the formula sheet they’ll get on the AP exam pretty early in the year and provide those on all of my assessments. This year, I have more students than usual trying to memorize equations, which tells me they aren’t seeing the formula sheet as a useful tool.

Bigger picture, I’ve been using some of the strategies for improving groupwork that I worked on in Physics last year, and I’m seeing good results, especially in my larger class. This year in general, I’ve been seeing more competitiveness than usual, but it’s been especially pronounced in my smaller class. The small class also has only two girls out of eleven students, and the girls have been vocal that it’s frustrating to often be the only girl in a group. I’ve got some students switching hours and both sections will have a pretty even gender distribution next tri, so I’m hoping that will help shift the tone in my smaller class.


We continued the two-stage final exam, where students complete a standard written final, then do a lab practical in small groups. I saw a lot of mistakes that I think are related to students struggling to differentiate different quantities and to recognize when a letter represents a variable and when it represents a unit. I need to give some thought to how I’ll help students distinguish those concepts moving forward.

My classes have been much quieter than usual this year, both in small group and whole class discussions. Over the course of the trimester, I’ve used some strategies, like giving more opportunity for small group talk before a whole-class discussion, that have helped. Over time, students have gotten more comfortable with each other and I’ve been able to cut back on the pre-discussions, but enough students are switching between hours for next tri that I’m going to go back to those strategies for at least a while as part of re-building the class culture.

Another aspect of the term transition I’m thinking about is the fact that around half of my students next tri will be coming to me from the other physics teacher. While we work very closely together and use the same materials, I consistently find many students do not transfer skills between our classrooms. I feel like I’ve got a good grasp on how to help students transfer skills like collaboration; I treat the start of the trimester the same way I treat the start of the school year and go back to building routines, norms, and a class culture with my students. I can back off quicker than in September, but it’s no less important than in the fall.

Where I feel stuck is with students who struggle to transfer physics skills between classrooms. I periodically hear from students that their class never learned a fundamental skill like drawing free-body diagrams or even entire topics, like balanced forces. Its tricky to coach a kid through that when I haven’t had a chance to build a relationship or get to know their strengths yet, so I tend to end up either helping to the point of giving answers or coming across as harsh about what students “should” know, neither of which is a good start. We’ll be starting tri 2 with unbalanced forces, so I’m giving some thought to how I can navigate these moments more productively. I want to try some open-ended approaches, like sketching a problem scenario I know was used in both courses and asking students very broad questions about what diagrams they might use. I’m also wondering if there are some ways I could involve other group members in these conversations to help them become more productive.

Days 51-55: Final Review

Next week are trimester 1 final exams. In both my courses this week, we wrapped up our last topic and started reviewing for the final.

AP Physics 1: Goal-less Problems

I really like Kelly O’Shea’s goal-less problems, so I decided to try that as a final review. I went through the released free-response problems and took the diagram and prompt from several that could fit with topics we’ve done so far this year. We focused on identifying applicable models, sketching additional diagrams, and reading strategies. Students especially liked a strategy to cross out information in the prompt that is accounted for in the diagram, especially once we started annotating diagrams to get rid of even more text.

An example of annotating a diagram and crossing out text that is accounted for in the diagram

Physics: Units vs. Variables

Students worked on, then whiteboarded a fairly standard final review packet with written problems. One of the biggest things I worked with students on is the difference between a variable and a unit, which has been a recurring challenge this year. For example, in the force of gravity equation, a lot of students are reading “g” as grams, rather than as 10 N/kg. I’ve been working on talking frequently about variables as representing a quantity and quantities as a number with a unit that describe something we can measure or calculate. Going into tri 2, I need to keep thinking about how to help students make sense of when a letter represents a quantity and when it represents a unit that is part of a quantity.

Days 46-50: Center of Mass & Vector Addition Diagrams

AP Physics 1: Momentum & Impulse

This week, we worked on developing the concepts of momentum and center of mass. We wrapped up a video analysis exercise (based on an article in The Physics Teacher by Taylor Kaar, Linda Pollack, Michael Lerner, and Robert Engles) where students track a system of two air pucks attached by a rod. Students made a lot of nice connections between the observed motion and Newton’s Laws, which lead to a lot of great discussion about what objects to include in a system to make sense of the motion. I also got to feel very cool demonstrating center of mass in an explosion with a track balanced on some blocks.

Physics: Vector Addition Diagrams

Students worked on solving problems with vector addition diagrams for balanced forces. We started with an activity I got from Casey Rutherford where students use pipe cleaners to rearrange the vectors on a free-body diagram before moving into problems on paper. A lot of my students struggle with the idea of rearranging the FBD, so starting by literally rearranging the vectors tends to be a useful stepping stone.

Days 41-45: Vector Addition Diagrams & Force Formulas

AP Physics 1: Vector Addition Diagrams

We wrapped up Newton’s 2nd Law with some problems combining vector addition diagrams and the 2nd law equation. I’ve been doing a much better job this year of combining vector addition diagrams with motion maps, which is helping students recognize the direction their net force needs to point.

Physics: Force Formulas

Students did labs to find formulas for the force of gravity and spring force. Most of the graphs had pretty good data and students did a nice job on the interpretation. On the force of gravity lab, several groups wrote their slope as 10 N / 1 kg to make it easier to give a “for every” statement during the board meeting, which was great. A lot of groups had some trouble “translating” the equation for their line of best fit into physics; a lot of it is getting tripped up by what a unit represents and separating that from what a variable represents. This is a challenge every year, and I need to keep thinking about how to help students make sense of the differences.

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.

Whiteboard with a data table with values for acceleration and force, a graph of force vs. acceleration, an equation for the line of best fit, and a value for the total mass the group used. The slope of the line of best fit is very close to the total mass.

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.