Energy

Days 105-109: Energy & Pendulums

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Physics: Energy

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.

Days 90-94: Impulse Problems & Energy Practical

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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

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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

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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 75-79: Values and Beliefs & Elastic Potential Energy

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This week has felt a little weird. Coming back from break, we’d gotten some messages to be ready to shift to virtual learning and all week the number of students and staff out went up, so everyone felt like we were in limbo. Near the end of my teaching day today, we got word that next week will be remote.

Physics: Values & Beliefs About Physics Learning

We started this week with a version of the values and beliefs lesson from Kelly O’Shea. There wasn’t as much discussion within groups as I was hoping (and it probably didn’t help that I was giving groups more space than usual to try and reduce my COVID exposure), but students had some great insights and really interesting things to say on the individual reflections I had them complete. One thing I felt like was missing in how I implemented this was some conversations about the costs and benefits of different views of physics and physics learning. One of the last things I had students do in their groups was pick some values or beliefs they think we should aspire to, and a lot of groups said we should aspire to do a better job of valuing memorizing facts and equations. I wonder if giving more space to why certain values and beliefs are or are not given a space in a particular classroom would have helped with some conversation about why they see memorizing as important and whether that is compatible with our classroom.

After two days of that, we spent the rest of the week on some problems about pushing cardboard boxes based on problems in Matt Greenwolfe’s More Models in Modeling materials. My goal was to refresh students on velocity vs. time graphs and free-body diagrams before we dive into momentum. There was a lot of great discussion, with lots of animated arguments. I was also really pleased at how often I could have students simply add a diagram, such as a system schema, to identify and fix their mistakes. I still need to work on how to facilitate a good whole class discussion with these problems, but I think part of the issue is I approach these problems with what I call consensus-building discussions, where I have every group whiteboard the same problem, then we try to resolve differences, but I don’t do this type of discussion very often so students don’t have much practice with it.

AP Physics 1: Energy

This week, we focused on going from LOL diagrams to doing calculations with conservation of energy. We started by doing a lab to find the equation for spring potential energy, which gives us all of the major energy types, then did a card sort that included equations based on just the types of energy and equations based on measurable quantities like velocity, mass, and height. The card sort made for a very nice bridge between the two types of mathematical representations.

Days 72-74: Unbalanced Forces & Kinetic Energy

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We had a short 3-day week to lead us into break.

Physics: Unbalanced Forces

We wrapped up unbalanced forces this week with a lab practical. I put a cart on a ramp, held in place by a string attached to a force sensor. Students had to first predict the tension in the string and next predict the time it would take the cart to travel between two photogates on the track once I cut the string. It was trickier than I expected for students to recognize that the tension in the string would be the same as the net force on the cart once the string was cut. Since that was an important idea in the paradigm lab we did this year, I left students to figure out that point on their own, but I think it would have been worthwhile to give students some questions or other structure to think through that aspect of the practical. We haven’t revisited velocity vs. time graphs lately, so I was very excited to see how well they did annotating their graphs and setting up equations to find the time.

A cart on a track with two photogates. The cart is tied with a piece of string to a force sensor and is held in place just before the first photogate.

AP Physics 1: Kinetic Energy

Students used Pivot Interactives for a lab to find the mathematical model for kinetic energy. Their data came out beautiful, but the introductory section of the activity didn’t do as much as I’d hoped to prepare students to collect data. This fits with a larger pattern I’ve noticed this year where students in both my courses don’t seem to make a clear connection between the pre-lab discussion (which the introductory section was similar to) and the actual lab. I think I haven’t helped students make a clear connection between the experimental design thinking we do in those discussions and what they will actually need to do in the lab. I’m giving some thought to how I can do a better job of showing how those discussions lead naturally to what students will be doing in the lab.

A silicone puck is levitating over a curved magnetic track. The puck is held in place near the top of the track by a small block of wood.

Days 62-71: Unbalanced Forces & LOL Diagrams

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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 103-106: Kirchoff’s Laws & Energy Card Sort

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AP Physics 1: Kirchoff’s Laws

Students worked on developing Kirchoff’s Laws this week. We started with PhET’s circuit construction kit, then got out the power supplies and resistors. Some groups had trouble recognizing the simulation and the physical lab as addressing the same concepts, but explicitly asking groups how their results compared seemed to help students make the connections. There was also some good discussion about why the results in the physical lab didn’t match the simulation exactly. A thermal photo showed some heat at the alligator clips, which lead to some conversation about whether the wires we were using were ideal.

Physics: Energy Transfer Card Sort

This week we worked on starting energy conservation problems. To help the transition from bar charts to problems, I turned some problems Kelly O’Shea and Mark Schober wrote for the New Visions physics curriculum into a card sort. Seeing cards with two versions of the conservation of energy equation seemed to help a lot of students see how to build equations from the bar charts, which made the problems much smoother than in the past.

Days 98-102: Circuits Intro & Energy Bar Charts

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AP Physics 1: Circuits Intro

We used PhET’s circuit construction kit to introduce some circuit basics and develop Ohm’s Law. Afterward, we used nichrome wire to test how the length of a wire affects its resistance. The data came out great, with groups that used thinner gauges of wire consistently getting larger slopes than groups who used thicker gauges. I usually skip over resistivity, but, at the AP reading last year, Wayne Mullins shared how he uses resistivity as a conceptual basis for Kirchoff’s Laws and I’m really excited to try that approach with my students this year.

Physics: Energy Bar Charts

This week was all about switching over to energy bar charts. I also noticed students are getting much more vocal during whiteboard sessions. I can’t figure out what’s behind it, but I’m really enjoying it. We’re getting close to the end of the trimester, and a lot of students switch between hours (or even between teachers), so I’m starting to think about how I can help students maintain this progress at the transition.

Days 68-72: Energy Practical & Pushing Boxes

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AP Physics 1: Energy Practical

This week, students worked on applying conservation of energy. We wrapped it up with a lab practical to find the spring constant of a popper toy. To help with what makes a good procedure, I had groups start by writing out the steps they were going to follow on a whiteboard. Then, they traded whiteboards with another group and had to follow the procedure they were given to actually collect data. One group came up with a nice strategy of writing out the equation they’d use in their calculations, then checking off each variable as they added a step to measure it.

Physics: Pushing Boxes

Students spent a lot of time this week on problems applying Newton’s 3rd Law and synthesizing Newton’s Laws, including some great problems originally from Matt Greenwolfe where students draw free-body diagrams and velocity vs. time graphs for boxes pushed across various floors. While there was some great discussion, I think these problems would have been more valuable much earlier in the forces model. In general, I think Newton’s 3rd Law feels like an afterthought in how we approach forces. With some shifts in what we’re doing early in this model, we could better integrate key elements of this model and reduce the need for doing some kind of synthesis at this point in the unit.