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.
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.
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.
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.
This was another short week. Parent-teacher conferences were on Thursday night, so Friday was scheduled as a professional development day.
AP Physics 1: Newton’s 3rd Law
This week our focus was on Newton’s 3rd Law. Students predicted which cart would experience a larger force during various collisions, which we then tested using a pair of carts with force sensors and hoop springs. In my grad class this semester, we’ve been doing a lot of talking about the ways language students use can mask meaningful understanding, which got me thinking about how I can make better use of students’ predictions. This year, I tried being very explicit that our task was to find the useful ideas in students’ predictions and to translate those useful ideas into the language physicists use. There was a great moment where a student said “So the force and the result of the force are different things, but we were treating them as the same”, which I couldn’t have planned better.
I also took a page from Brian Frank this week and used some magnetic hooks for an easy setup of a static forces lab practical.
Physics: Newton’s 1st Law
This week was about developing the idea of a force and Newton’s 1st Law using interaction stations and the bowling ball lab. A few students were resistant to actually trying the bowling ball lab this year, rather than actually testing whether what they expected worked, so I had to push some groups to really explore getting the bowling ball moving with a constant speed. Once they got started, however, there was some great discussion.
This was a three-day week since public schools closed on Thursday and Friday for the state teachers union conference.
AP Physics 1: Vector Addition Diagrams
Students started the week by doing Kelly O’Shea’s forces representations card sort. I used the card sort to introduce vector addition diagrams, and students easily recognized key aspects of the VAD. The rest of the week, we worked on applying VADs to solve problems. They are successfully applying the VADs, but aren’t feeling confident in their skills just yet.
Physics: CAPM Practical
After wrapping up some problems using the constant acceleration model, students started working on a practical to figure out where to start a marble on a ramp so that it lands in a passing buggy. We ran out of time for students to test their calculations. While students made good progress, many are uncertain of their skills; I’m hoping that completing the practical on Monday will help them build confidence.
This week was all about figuring out the formulas for gravitational force, spring force, and friction force, then practicing combining them with free-body diagrams. After doing some fairly standard labs to develop the formulas, students did a version Kelly O’Shea’s problem solving stations. I’d like to add a station using the force of friction, but need to make sure there’s a good way for students to check their answer.
This year, I’ve been working on keeping my pace on track, and most students are keeping up. I always have some students who start out goofing off during the daily work because its not graded, but the majority of them are figuring out they need to stay engaged, which is great because students are deciding for themselves that the daily work is valuable and my retake policy means they aren’t stuck with a grade based on choices they made early in the term! The problem is I’ve also got a few students who I see starting a cycle where they are missing pieces because of goofing off, then struggle with what comes next, and disengage more out of frustration. Before students become stuck in that cycle, I need to give some thought to how to help those students feel a greater sense of control over their learning. I think on Monday I might spend some time talking as a whole class about strategies for when students are feeling stuck or frustrated. I’m also trying to be conscious of how I approach those students, trying to keep my focus on communicating I’m available to help rather than chiding them for being off-task.
Physics: Constant Acceleration Representations
Students practiced using constant acceleration representations. A lot of them are having trouble connecting what we’re doing now to constant velocity representations, which happened last year, as well. I need to put some thought into how we structure this unit to help students see how we are extending their skills, rather than starting something completely new.
In whole-class discussions, students are still pretty quiet, though I’m seeing signs of progress. I’m hearing a lot from students how much they like mistakes whiteboarding, even if just a few students are responsible for most of the questions during those activities. There was a great moment where a group presenting said they didn’t want any questions from a peer who’d been very vocal during the other presentations, and he responded “That’s a great idea!” When no one raised their hands, a member of the group started calling on some of the other people she knew had a good grasp of the problems, but rarely speak up. It was a pretty awesome moment.
This week was a little goofy. Students were off Friday for a staff development day and it was homecoming week, so classes were shortened on Monday and Thursday for festivities.
AP Physics 1: Free-Body Diagrams
This week was all about Newton’s 1st law. We started with the bowling ball lab to come up with a formulation of N1L, then worked on representing forces with free-body diagrams and system schema. Both sections had mistakes whiteboarding sessions that were overall really good. There was a debate about whether a projectile should experience air resistance that had a lot of good thinking. We ended up grabbing a softball out of the storeroom and capturing an image of it rolling in Motion Shot to see if it had a constant velocity. There was a much more intense debate about air resistance than I’ve seen before and I think the group presenting felt like it became a “gotcha” moment. I need to think about how I could have intervened differently in that discussion to shift the tone it took on.
Physics: Constant Acceleration Model Building
Students used video analysis to produce graphs of the motion for an object on a ramp. I was ornery about making students attempt to follow a reference guide I made before I’d help with the technology, which made it a lot easier for me to spend time with students who needed help troubleshooting. The results were better than when I’ve used photogates, but still fairly messy. I think part of the problem is, regardless of the approach, students rush on key pieces and get sloppy data as a result. I need to think about how to slow my students down at key steps. It was also tough to get students to speak up during the board meeting, even with doing a gallery walk and jotting down some observations with their group beforehand. I’ve got more students than usual who underestimate how much they know and are wary of jumping in as a result. I have some work to do on increasing the social safety in my classroom and helping students recognize their contributions.
Students also did Kelly O’Shea’s CAPM card sort. Interestingly, even though this fell on the day of our homecoming pep fest, students were overall very engaged in the activity. I saw a lot of the same students I struggled to get to speak up during the board meeting asking great questions and sharing ideas during the card sort. I think the small group setting was a factor. I need to give some thought to what else made students comfortable speaking up so much in their small groups and how I can bring that to whole class discussions.