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.
We had Friday off this week. I think staff and students alike were very happy to have a long weekend.
Physics: Popper Hoppers
This week we wrapped up energy. After finishing the bouncy ball evidence-based reasoning from last week, we got out the popper hoppers to use energy to find the spring constant of the toy. We haven’t done as much having students decide what measurements to take as I’d like, so students struggled a little at first with what measurements to take. I showed them a strategy from one of my past AP students wo would write out the equation she was going to use to solve for the target variable, then put check marks next to each of the other variables once she had a step in her procedure that would get her a value for that variable. That was exactly what students needed to get a solid plan for the practical.
AP Physics 1: Unbalanced Torque
This week, we worked on unbalanced torque. We used another Pivot Interactives activity (Disclaimer: I work for Pivot Interactives as a content writer. This activity should be published soon!) since I haven’t had a chance to play with the hands-on equipment we purchased for rotation in fall 2019. I’m trying to be pretty conscious of making explicit connections to unbalanced linear forces, both to make sure students aren’t starting from scratch in their understanding and to embed review of earlier topics. Students are seeing those connections pretty clearly, which is great to see.
I also started a countdown to the AP Physics exam on my whiteboard, and noticed students are more focused when working problems. I think the countdown is adding some sense of urgency to what we are working on.
The biggest task this week was a lab to determine the equation for kinetic energy. On some recent labs, students have struggled to get good data. I think part of the issue is many don’t buy into the idea that knowledge should come from the labs they do, so they don’t invest the effort or attention into getting good data, which makes it hard to see how it leads to physics concepts or equations and becomes a self-reinforcing cycle I wanted to interrupt with this lab. We talked a little about what I observed and my hypothesis, then I re-did the gravitational potential energy lab as a demo and made a point of discussing the things I was doing to get good measurements and check the quality of my data as I went. When we were getting ready to whiteboard, I also checked in with groups to make sure they had quantities on the correct axis and were seeing that they needed to linearize. The result was data that really nicely showed the quadratic relationship between kinetic energy and velocity and most graphs even had slopes very close to half the mass of the carts students used! A lot of students were really proud of their results, which was great to see and I’m hoping will encourage them to continue those good data collection practices.
AP Physics 1: Centripetal Force
I like to ignore the College Board’s recommendation to do centripetal force as unit 3 because it is such a nice opportunity for built-in review of a lot of ideas about forces. We started by spinning some rubber stoppers on strings to talk qualitatively about how we could change the force in the string before moving over to Pivot Interactives to collect quantitative data (disclaimer: I am a content writer for Pivot Interactives). Next, we used an activity I originally got from Lucas Walker using exoplanet data to find the law of universal gravitation. Students are making the connections I want them to, but I can tell they are starting to feel some fatigue. I typically rely a lot on Pivot Interactives for this topic since we don’t have much equipment, but students got pretty into the brief hands-on activities we did this week, so I think I should make sure to keep working those in to help my students stay engaged these next few weeks.
Students did a lab to introduce energy where they pulled carts up ramps at different angles, always raising the cart to the same height above the table, then measured the average force they needed and the distance they had to pull the cart for each angle. Then, they sketch force vs. distance graphs and see they always have the same area. The data was rough enough this year that students could see that a steeper angle required a larger force and a smaller distance, but the areas varied a lot. We’ve had a few labs lately where the data came out pretty rocky. I think part of what’s going on is it’s been tough this year in general for students to see connections between what happens in the lab and the physics concepts we are learning. If the labs are something disconnected from the rest of your learning, why would you invest time and attention into collecting high-quality data? We’re also at the end of a trimester when more students than usual are scrambling to raise their grades after an unusually challenging term and the February doldrums have been hitting everyone harder than usual, so students have less attention and mental energy to go around than usual. Aside from the final, we won’t have any more labs until tri 3, which is a good time for a fresh start. In the meantime, the other physics teacher and I need to do some thinking about how we will continue to draw connections between labs and physics concepts and make sure students have what they need to get good-quality data.
AP Physics 1: Pendulums
This week, we started working on simple harmonic motion. For the first activity, students used a video from Pivot Interactives that shows a pendulum, a cart attached to springs, and a spinning disk all in synchronized simple harmonic motion. Students made position vs. time graphs for each object, which always works well for some discussion not only of how the motion of all three is similar, but to establish some important ideas like the non-constant force and the repeating patterns in the motion of each object. After that, we dove into a deeper focus on pendulums by doing a lab to find the factors that affect the period of a pendulum. This model is going to be split over spring break, which got me thinking about how I currently have the unit structured. Right now, I have one standard for pendulums and one standard for springs. But, especially since I start by emphasizing how similar those two kinds of motion are, I wonder if it would make sense to instead have a standard about using multiple representations like motion graphs and energy bar charts to describe simple harmonic motion that includes both springs and pendulums, then a separate standard on the mathematical relationships and factors that affect the period which also applies to both pendulums and springs. That seems like it would better represent the different kinds of thinking I ask students to do over the course of the unit.
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.
A lot of this week was working on calculations for constant acceleration. My students are struggling more with the algebra than in a typical year and it sounds like other teachers are seeing similar things. They are doing some great mathematical thinking, but just aren’t as comfortable as usual with common processes like making a quick graph based on an equation or doing algebraic manipulation. I tend to trust that once students see what math they need to do, I can expect them to get through the math without much support. This year, I need to make sure I’m putting attention to helping students develop their math skills alongside the physics. My course on STEM integration theories last fall got me thinking about how I can go beyond math as a tool in my classroom to instead support meaningful math sensemaking, and this year will be a good push to put what I’ve been thinking about into practice.
I also graded the first lab write-up this week, and my students did much better than I usually see on the first lab write-up. In general, this group of students are stronger than usual at explaining their thinking and the kind of writing I usually look for, which is fantastic in a course like AP Physics 1. I’m really excited to be able to help students build their already strong skills.
Physics: Technology Tools
This week, we wrapped up constant velocity by having students do activities with Vernier Video Analysis and Pivot Interactives. For the video analysis assignment, we had students record a short example of something they thought was constant velocity, then use the video analysis results to test the claim. Since the focus of this activity was on interpreting the position vs. time and velocity vs. time graphs, I think it would have worked well when we were preparing to transition from interpreting diagrams to doing calculations to help break up the stretch we had of paper and pencil problems.
A big goal of these activities was to introduce students to tools we’d been using in a context where students were already pretty solid on the content. When introducing technology, I do a minimal demo and instead provide students with a user guide or other detailed instructions on how to use the tool. I have a lot of students who are more comfortable with a walkthrough, so I spend most of the hour on my feet answering questions by reminding students to use the resources I provided them. These days are tiring, but they pay off with students quickly becoming very independent with these tools as they learn to navigate the user guide or help documents. However, I’ve developed some new back issues in the last year and a half and am very aware today that I can’t currently bounce around the room as much as I used to. We are using video analysis again on Monday, and I need to give some thought to how I will balance ensuring students have the support they need and feel like I’m available for questions with managing my own health.
This is the last topic students need before the AP Physics 1 exam. Students built the model using a Pivot Interactives activity where a marble is fired at a block. One of the questions I asked is whether the distance between the block’s center of mass and the point where the marble strikes has any impact on whether the momentum of the block-marble system is conserved, and I was surprised to see most of my students said yes. I’ve done this activity in the classroom, and I underestimated the importance of the conversations students have on their way to answering the question. I think if I had explicitly prompted students to use tools like an SOS diagram before answering, they would have been more likely to recognize momentum is conserved.
Physics: Pendulum Equation
Students wrapped up the pendulum lab. At the end of last week, I noticed in a discussion board that a lot of students saw their period vs. length graph as linear, so I made a short video talking about how the intercept affects that interpretation. Their first assignment this week was to finish their data analysis and answer a few questions. Most of my students still said their period vs. length graph was linear, which tells me they either didn’t watch the video or didn’t incorporate that information into their work. For my grad class, I’ve been reading about constructivist learning theories in online science courses, and one of the big challenges is most platforms emphasize results and answers, rather than process. Without feedback on their process, students are likely to resist changing a conclusion they’ve arrived at. I need to think about what it looks like to create the space and the expectation for students to share their process in an online environment.
Chemistry Essentials: Balancing
Students have been gradually catching up on old work thanks to the pause I took last week. There’s still a lot of students who aren’t taking visible steps to get caught up, but I’m glad to see some progress.
This week’s assignment was to use PhET’s balancing chemical reactions sim to get an idea of what it means for a reaction to be balanced. I usually start balancing with this activity, and it was really nice to have something that translated so easily to an online environment. Only a few students have completed the assignment so far, but those who have are showing a solid conceptual understanding of what it means for a reaction to be balanced.
Students used Pivot Interactives to find a relationship between torque and angular acceleration. The activity has several different bicycle wheels, which lead to some good discussion on the forum as students first compared their results to someone with the same wheel, then compared results to someone with a different wheel.
In both the questions I got about the activity and in the grading I was doing this week, I saw a lot of students struggling with the distinction between different terms related to gravity. That’s been an on-going challenge this year that I think is related to having some students who use a lot of verbal shortcuts. We’ve made a lot of progress on that front this year, and a lot of students were joining me in pushing back whenever someone used imprecise language. I think with out that consistent feedback on language, some students are falling back to old habits. I’m giving feedback on language in students’ written work and sent out a vocab review to all of my students, but am thinking about other options.
Students used Pivot Interactives to collect data we’ll use to get the equation for the period of a pendulum. This week, we had students collect data, then post their graphs and answers to a few questions to a forum. Next week, they’ll start by linearizing the period vs. length graph. Based on the forum, I’m glad we split the lab up. In the questions, students recognized angle and mass don’t affect the period and correctly explained why the period vs. length graph should have a zero intercept. However, most students described their period vs. length graphs as linear in spite of the large intercepts. Using the discussion and splitting up the lab gave me a chance to catch the issue and record a short video before students started their linearization. It’s been hard to be responsive when I have almost no contact with my students right now, so it felt good to have this opportunity to shift my instruction based on students’ current thinking.
Chemistry Essentials: Pressing Pause
The representing reactions summative was due on Tuesday, and only two of my students had turned in work for the module. Rather than sticking to my plan to start balancing, I pushed everything back so that students have an extra week to catch up before their next assignment is due. I also spread out the remaining work in an effort to reduce the workload. We’re shooting for each class to have around 90 min of work per week, so I’ve been assigning what would take around 30 to 45 min in the classroom each week, but the students I’ve heard from are spending around 3 hours a week on chem. I’ve only gotten work or heard from a few kids since Tuesday, but even if just a few more kids get a credit required for graduation as a result of this week’s adjustments, I’m happy with my decision.
My district requires all teachers to have students complete a teacher evaluation survey. Since it’s ideal to have students complete it without the teacher in the room, I picked today. Teachers chose which classes to give the survey to; since AP Physics 1 is the only class where I keep the same students all year, I decided to survey them. While there are certainly flaws in student evaluations, I am interested in seeing the results to get another view of the culture in my classroom.
Physics: Curved Mirrors
Students did a lab to play with curved mirrors to start building some ideas about the images formed by concave and convex mirrors.
Students used Pivot Interactives to get one more look at some of the different reaction types before their quiz. Along with a single replacement and a double replacement reaction, I had students use what they know about synthesis reactions to finally explain why burning steel wool gets heavier.
Students whiteboarded their results from yesterday to get to a definition of angular momentum, as well as the relationship between torque and angular momentum. They made nice connections to conservation of linear momentum as well as impulse.
Physics: Ray Diagram Mistakes
We did mistakes whiteboarding with yesterday’s ray diagram problems. Students were doing very well figuring out which rays were critical to the problem and catching each other’s mistakes.
Students used Pivot Interactives to do a lab involving limiting reactants. Since lab data makes it tough to use particle diagrams, I tried having students convert their balanced reaction equation into “for every” statements. A lot of them were pretty successful using those statements to make sense of the other calculations I asked for.