Simple Harmonic Motion

Days 92-96: Springs & Impulse

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On Friday last week, I found out our new physics teacher would be starting this week. I went into this year expecting to be doing my role as science content specialist full-time and it has been tricky to juggle that work with my teaching. I’m excited to be able to focus more on my role, but it is hard to be getting ready to leave students I’ve been with for a while. The new teacher shadowed me this week so he could start getting to know the students and the curriculum. We will then be co-teaching until the trimester ends on March 10. Trimester 3, he will take over Physics completely. I’ll still be in AP Physics 1 on occasion up through the AP exam since this is our new teacher’s first time doing AP and it’s a lot to get the hang of in a short amount of time!

AP Physics: Springs

Students conducted an experiment to find factors that affect the period of a spring. The data was kind of rough, mostly because they were having trouble getting the springs to oscillate nicely. We still had enough good data in the class that we were able to figure out all the things we needed to. On both this and the pendulum lab, I was really pleased with how students used the intercept of their graph to figure out they needed to linearize. After the lab, we worked on some problems with representations for simple harmonic motion. It was a lot of fun to see students putting together forces, energy, and motion graphs to make sense of simple harmonic motion and they made a lot of great connections.

Physics: Impulse

This year, we tried a new sequence for momentum where we started with conservation of momentum since looking at a system that includes both objects in a collision is a really strong motivator to learn momentum. This week, we did Newton’s 3rd Law and used that combined with Newton’s 2nd Law to derive impulse and start thinking about individual objects. This was a tough transition for a lot of students to make and I’m wondering about ways we could make it smoother in the future. One thought is we don’t emphasize system choice in Physics, but that is pretty key to thinking about impulse. I’m not sure what to do with this thought yet, but definetly want to keep it in mind.

Days 87-91: Pendulums & Conservation of Momentum

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AP Physics: Pendulums

This week we started simple harmonic motion. We started by using a video on Pivot Interactives that has a pendulum, a glider on a spring, and a spinning disk that all go through simple harmonic motion with identical periods and amplitudes. Students plotted position vs. time and velocity vs. time graphs. When we shared the results, the students in calculus made some great connections to derivatives. We then moved into a lab to find the factors that affect the period of a pendulum. This is one of the labs where I felt like the hard work learning how to do an experiment really paid off as students worked pretty independently and got great results.

Physics: Conservation of Momentum

This week students worked on practicing conservation of momentum problems. One of their tasks was to figure out an unknown mass using results from a collision. One thing that has been tricky every time we do this practical is students sketch bar charts for what they want the collision will be, such as having both carts come to rest after a collision, but have trouble adjusting if their bar charts don’t match the actual collision. I think this comes down to many aren’t thinking of momentum bar charts as something that describe a physical event. I wonder if it would be helpful to do an activity where students do various collisions between pairs of carts, but focus only on representing those collisions with bar charts.

Days 167-170: Pendulum Practicals & Final Project

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This was the last week of school for seniors! Since they are around 90% of my students, this was the last week of instruction in my classes. Next week, the juniors in my classes will have time to finish anything they still need to for my class or prepare for finals in their other classes.

Physics: Pendulum Practicals

This week we did two lab practicals using pendulums. First, we had students determine the length of a pendulum using only a stopwatch, which went really smoothly. Next, we had students figure out where to start a buggy so that the pendulum bob would collide with a passenger in the buggy. The big thing I noticed was students treating the period of a pendulum as three different equations, depending on which variable they were solving for. This fit with a general pattern this year of students struggling with using math in physics. While I think the unique challenges of last year are a factor, I think it would also be worth looking at our curriculum to see how we could do a better job of not just using math, but helping students develop a conceptual understanding of the math we are using. I won’t be able to work on that directly next year since I will be out of the classroom working as a high school science content specialist, but I’d like to think about how I can support teachers interested in that work. There will also be a high school math content specialist, and I think it will be worth having some conversations with him to think about how our departments could collaborate.

AP Physics 1: Final Projects

Students met with me about their final project drafts, then presented them to the class. I feel like while these students are phenomenal in small groups, I’ve struggled to build a whole-class community this year. During the presentations, however, there was a lot of joking around from both presenters and the audience, and several presentations included references to Throckmorton, who appears in many of our problems. I think we had more of a whole-class community this year than I realized, it just looked different than in previous years. It was really nice to have that so apparent on our last day together.

Days 162-166: Pendulums & Final Projects

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Physics: Pendulums

We worked on an assortment of pendulum problems this week. The packet starts with some problems that focus on using representations like free-body diagrams and energy bar charts to describe the motion of a pendulum. After that, we shifted to lots of algebra using the equation for the period of a pendulum. With the way our packet is set up, we don’t have students do much thinking or reasoning with the diagrams they sketch. I think with this unit, I’d like to revise our packet to get more emphasis on conceptual thinking about pendulums.

AP Physics 1: Final Projects

Students continued working on their final projects. The projects this year are heavy on calculations to describe scenes in movies or moves in video games. I usually have more projects that involve real-life data collection, but I think this is partly a factor of doing a a shorter project than usual since the AP Physics 1 test was so late this year, so students had less time to brainstorm and to carry out their projects. That said, I am having a lot of fun talking with students about their projects and hearing all the cool thinking they are doing.

Days 118-122: Energy Bar Charts & Springs

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This week, we came back from spring break and started trimester 3.

Physics: Energy Bar Charts

This week we focused on drawing energy bar charts. Students have struggled to connect representations, so I tried starting by having students draw the more familiar energy pie charts. Then, we got out the Mathlink cubes to use as a manipulative representing the types of energy (an idea I think I first saw in Scott Hertting’s article in The Physics Teacher). Once students had rearranged the cubes to represent at least two different snapshots, I had them sketch how they arranged the cubes on a bar chart. One thing I was really excited about is as the week progressed, I had some students ask if they could keep using the cubes, which tells me they were a useful tool. I also saw a lot of students sketching energy pie charts to help figure out what the bar charts should look like, which tells me they are connecting the two representations when seeing relationships between representations has been really challenging this year.

Cubes in three stacks on a whiteboard. Each stack is labeled with a type of energy.

AP Physics: Oscillating Springs

Students did a lab to find the equation for the period of a spring, then we dove into some problems. Students did really well with the problems focused on representations and showed a lot of growth from earlier this year on the problems from the College Board’s AP Physics 1 workbook. The workbook problems included a lot of predictions about how various factors would affect the period of a spring, so we used a spring to connect a motion encoder cart to a force sensor on a track so we could change the angle the spring was at, as well as factors students had already tested like mass and amplitude. I also made sure to use this as an opportunity to review some basics on motion graphs since exam day is starting to loom.

Days 110-112: Energy Pie Charts & Pendulum Practical

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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 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.

Distance Learning Week 8

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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.

Distance Learning Week 7

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AP Physics 1: AP Exam

With the AP Physics 1 exam on Thursday, I decided not to assign anything so students could focus on reviewing, especially since many of my students were taking other AP exams earlier in the week. The couple of students who checked in after the exam said they felt really good about how it went, which was great to hear.

Physics: Pendulum Assessment

Students worked on applying the equation for the period of a pendulum to some problems and a short summative assessment. Students felt really good about this module; it involved a lot less conceptual knowledge than previous modules and didn’t require students to connect to many old ideas, which I think made it easier. I recently heard from a few students that between being out of school for all of March and not having access to old packets they’d left in their locker, they were having a very difficult time with the fact that the first two modules revisited old concepts, like motion graphs. I think it’s worth putting some thought into how we can do a better job of giving kids resources for going back to old ideas during distance learning.

Chemistry Essentials: Balancing

Students worked on some problems balancing chemical equations. The couple of kids I’ve talked to are now buying in to particle diagrams since they make balancing so much more concrete. Prior to balancing, particle diagrams were the first truly new content we’d done via distance learning, and I had some students who really pushed back on trying to get them down. It’s great to see some of those same students now recognizing the value of that representation.

Distance Learning Week 6

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AP Physics 1: Angular Momentum

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.