Forces

Day 137: Universal Gravitation & Glacier Video

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After no classes yesterday due to state testing, we got back in the swing of things today.

AP Physics: Universal Gravitation

Today continued quick and dirty coverage of some topics on the AP exam that we haven’t really addressed yet. Today, I asked students whether uniform circular motion or free fall is a better description of the Moon’s motion, and students went very quickly to wanting to find the acceleration, so I gave them the Moon’s period and orbital radius, and got out of the way. This served as a nice refresher on circular motion. Once students got a tiny acceleration, we reasoned that a 1/r2 relationship might make sense for gravity and checked that against gravity at Earth’s surface and get to the Law of Universal Gravitation.  Then, since most of my students saw Coulomb’s Law in chemistry, we used the parallels with gravity to make sense of that formula.

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Earth Science: Glacier Video

With conferences tonight, I went ahead and showed the video in the curriculum for today. The video was about the data sources glaciers can provide, which got me thinking about how to have students explore those data sources in the lab. For glacier movement, I’m wondering of something like gak could be used to simulate a glacier, maybe with food coloring drops or toothpick flags to track specific points. For the ice cores, I was thinking it would be really cool to find some scale photos of actual ice cores, especially if I could find a way to have students compare the core data to weather data for that year. Of course I thought of all this while watching the video, rather than last night while I stared at the curriculum materials. Oh well.

Day 114: Final & Project Presentations

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Today and tomorrow we are on a special schedule for final exams.

AP Physics: Final Exam

Students are taking a practice AP exam for their final. Since we have 90 min class periods during finals, they did a modified free response section yesterday on our last day with a regular schedule. Tomorrow, during their final exam period, they will take the multiple choice. I already know they are going to struggle on a few specific questions because we have not done much thinking in terms of the center of mass of a system, so, when we review, I’m planning to re-do a couple of topics focusing on those kinds of problems.

Physical Science: Project Presentations

I cut down the written final to fit in a single class period, then had students present their designs to the class during the extended period. Afterwards, students did some reflecting on the project, focusing on how they functioned in a group. A lot of the reflection would be more meaningful if students weren’t going to be completely reshuffled the next regular day of classes, but they were pretty engaged nonetheless. Students said they much preferred this over doing the written final today since it was lower stress and gave them a break from sitting in silence all day.

Day 112: Model Summaries & Peer Review

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AP Physics: Model Summaries

Students made model summaries for the rotation version of key models so far. Students seemed to find it useful to remind themselves what tools are available to think about these models. Afterwards, students worked on some goal-less problems to reinforce the importance of starting a problem with what models apply. Students were really pleased when they realized some of the problems worked equally well with energy or with a combination of constant acceleration and forces.

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Physical Science: Peer Review

I had groups pair off to share their presentations and give some feedback. My strong groups made good use of the time and I heard a lot of nice feedback, but my other groups could have used more structure. Next time, I think I will provide students with hard copies of the rubrics to fill out to give them a little more accountability and focus their feedback.

Day 111: Model Summaries & Presentation Work

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AP Physics: Model Summaries

Today and Monday are dedicated to review for final exams. One of the problems on yesterday’s assessment is from last year’s AP Physics exam, so I gave students a copy of the scoring guide for that problem and some time to see how they measured up against the College Board criteria. Students responded positively and said it helped them understand what the graders are looking for.

Afterward, I assigned each group one of the four major models we’ve covered so far (constant acceleration, forces, momentum transfer, and energy transfer), then had them whiteboard a summary of that model. Once groups finished, we did a gallery walk so students could have a chance to review other models. Students said this helped remind them of tools they’d forgotten about. I think on Monday, I’ll come up with some problems for them to practice picking appropriate tools.

model-summary

Day 110: Fun Test & Presentations

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AP Physics: Assessment

Students took their energy assessment. For the first time, I had multiple students tell me the test was fun, which was especially good to hear since I included a free-response problem from the 2016 AP exam. My PLC has been focused on experimental design this year, and I’m enjoying seeing that payoff in my students not only doing well with that skill, but feeling confident enough that they can enjoy applying it.

Physical Science: Presentations

Students worked on presentations to make the case for their cargo carrier design. I gave students a template a colleague made last year to help students make sure they are connecting the science to their design, but, after watching them work, it feels like too much scaffolding. I made much better use of a graphic organizer for evidence-based reasoning than in the past and did more to embed that skill throughout the course, and I think framing the presentation as evidence-based reasoning on a bigger scale may have been enough. I need to think about what that might look like next year.

Day 109: Collision Types & Testing Round 2

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AP Physics: Collision Types

Students worked some problems using elastic vs. inelastic collisions. They are feeling very confident about energy, which is great to see, and several students are thinking about how they could use energy to work problems we’d done earlier in the year, which is fantastic.

As a side note, registration for our AP exams ends tomorrow, and I’ve offered doughnuts to the first class to get 100% registered. Its been surprisingly effective and I’ve currently got the highest registration rate. I need to remember to give the same challenge next year.

Physical Science: Testing Round 2

Students tested their second design. There was a nice variety of tests, including one group that had a tray of ice at the bottom of their ramp to simulate weather conditions. Most groups tried at least one collision besides the head-on we’d done before. One group asked if they could use bubble wrap to simulate a bumpy road. While the trucks are heavy enough that I don’t think the bubble wrap did much, I like the idea and am thinking about what might have worked better.

Since we only have four ramps, I assigned groups with similar tests to the same stations and directed them to figure out how they would share the equipment. It was more chaotic than the first round of testing, but that’s to be expected. I might scaffold them a little more on making that plan next year.

 

A bumpy road
Rear-end collision

Day 108: Collision Types & Building Again

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AP Physics: Collision Types

We whiteboarded the results of Friday’s Direct Measurement Videos to get to the definitions of elastic and inelastic collisions. A lot of groups tried to answer purely conceptually, in spite of some quantitative questions on the activity. I think these groups were treating each question as separate, rather than thinking about how one answer could help them with the next piece of the activity. I want to make better use of lab notebooks (most likely starting next year) as a reflective tool, which I think might help students see more connections between problems.

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Physical Science: Building Again

Students worked on their second round of building. I upped the cost of paper cups, which were the most popular material on the first go around, which lead to a little more variety in egg holders. I also did another round of visiting each group and asking them to explain their design choices using Newton’s Laws, and I can tell students are getting more confident with this skill.

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Day 107: Collisions & Test Design

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AP Physics: Collisions

Students use a pair of Direct Measurement Videos, one of a collision between two billiard balls and one of a heavy disk tossed onto a cart, to explore changes in momentum and kinetic energy in the collisions. I haven’t done as much with uncertainty as I’d like, so I was very pleased with how clearly students were talking about it to decide if their values were “close enough.” I had students sketch momentum SOS and energy LOL diagrams, but students weren’t paying as much attention as I’d hoped to whether there were any dissipative forces present, so next year I want to do a better job of getting students into that habit. I was thrilled, however, when a student used some proportional reasoning to convince herself that you cannot conserve momentum and keep a constant kinetic energy when the objects are moving together after the collision. I was also pleased by how many students were interested in trying to explain the billiard ball that just spins in place right after the collision.

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Physical Science: Test Design

Students began working on designing a second iteration of their cargo carriers. To encourage new designs, I increased the cost of paper cups (the most popular component on the first round) and shuffled groups. We also talked about the limits of testing just the front-end collisions, and tasked students with coming up with their own tests for this round. The discussion was a little trickier this year than in the past; we dramatically upgraded the trucks the cargo carrier attaches to this year and the old trucks would pretty reliably tip over or roll off the side of the ramp at least once per class, which gave a nice tangible example of the test’s limits. That didn’t happen at all this time, so next year I might take off the rails we put on the side of the ramps to try to encourage some failed tests.

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Day 106: Energy & Crashes

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AP Physics: Energy

Students whiteboarded CER statements for various energy questions, including their answers to where the bouncy ball loses energy and why the tiny bouncy ball from a seismic accelerator flies off. I really liked that different groups tended to take different approaches, which made for some good sharing of ideas once whiteboards were ready and made students very confident in their responses.

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Physical Science: Crashes

Students attached their cargo carriers to trucks, then sent them down to ramps for head-on collisions. My students usually get pretty animated on this day, which usually includes a lot of bragging about how well they expect their design to do. For some reason, a lot of students in this class were expecting their eggs to break right away, including some students who were filled with confidence yesterday, and the class as a whole was very anxious and nervous. None of the points come from how well the design performs, so it was interesting to see how much tension some students were feeling, anyway.

carrier-1

Day 105: Dissipated Energy & Building

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AP Physics: Dissipated Energy

Students analyzed video of their bouncy balls and collected evidence to argue whether the energy is primarily dissipated by air resistance or by the impact with the table. There was a nice variety of approaches and I was pleased by how many students went back to the fact that we neglected air resistance during projectile motion to make a prediction about whether it should matter here.

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Physical Science: Building

Students worked on building their cargo carriers based on yesterday’s designs. To help keep the focus on the science behind their designs, I stopped by each group and used a dice to pick someone to tell me how Newton’s Laws support their design decisions. For the first time, I had several tables where students were hoping they would be the one picked because they were excited to talk about their group’s work, which was fantastic!

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