Days 38-42: Forces

Physics: Balanced Forces Intro

This week we started balanced forces. Since making sense of labs has been really challenging for students this year, I put a lot of thought into how I wanted to frame the lab activities. We started with the bowling ball and mallet lab, where I really emphasized the motion maps to draw connections between forces and what we’d already been learning. In the past, I’ve had some groups who record what they expect, but never actually try tapping the bowling balls with mallets. To prevent that, when I introduced the lab, I emphasized that I am not expecting students to know what will work and that this lab is about observation, not prediction. Motion Shot is still working on my phone, so I used it to help convince some groups that a bowling ball moves at a constant velocity without any interactions, but I wish I’d pulled out the app for every group that was struggling with drawing motion maps; I think that did a lot for the groups I used it with to connect what was happening in the classroom to the more abstract representation. We followed up with some interaction stations based on Brian Frank’s introduction to forces, which I again introduced by taking more time than usual to talk explicitly about the purpose of the activity and what I expected students to know.

AP Physics 1: Unbalanced Forces

This week we started unbalanced forces with the modified Atwood’s machine. We used Vernier motion encoders to collect the data, and I found students were pretty overwhelmed by the technology. It occurred to me that this was their first experience using force sensors and they’ve only used the motion encoders once before. The lab took longer than I’d hoped, though students still got reasonably good data. I think next year I need to plan to get out these materials for some of the simpler labs where I default to using tools like spring scales with the mindset of getting students practice with the probeware before labs where the data collection is more complex. I’ve done that in the past, but am a little out of practice on teaching students lab skills!

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