# Day 36: So Many Circles. Also Pigs.

Tuesday, Oct 24

Physics: Started circular motion. I hate the word “centripetal” if that wasn’t clear from the Day 35 post, but the Hewitt book uses it a lot, so I couldn’t get away with just not saying it. We did the “swing a thing above your head” circular motion lab with a spring scale taped to a meter stick, a string attached to the scale and then threaded through a plastic tube and tied to a rubber stopper. Tomorrow is exam review day, so we’ll go over the lab itself on Thursday.

Honors Physics: Flying pig lab! Since we were doing a conical pendulum analysis yesterday, today I pulled out the flying pigs and had them find the velocity two ways. It was basically the Conceptual Physics Lab from the manual, but I didn’t give them the step-by-step instructions and they had to figure out what to measure and how. They also had to figure out how to hang the pig up and get it going at all, because I couldn’t figure out a good, consistent way in the hours I fooled around with it before class. So, it became part of the lab, and each group came up with a different way of doing it, and we’ll see how that comes out in the data. I made sure to put on my Flying Pig Lab Safety Equipment before demonstrating how the pig works.

AP Physics: The first class is learning about forces that make things move in circles. Again, I avoided using the word “centripetal” and just talk about forces and acceleration that are perpendicular to motion and change direction. That is so much more clear. One of the students said it, and I pointed at him and said, “I don’t ever want to hear those words come out of your mouth again.” They did some vertical circle analysis

The second class did the in-class investigation to discover the relationship between length and period. One of the punks looked up the equation and wrote it on the board, effectively ruining the whole point of it, which means I need to re-think that entire activity, as well, and figure out something with less opportunity for ruining things. On the whole, I don’t know how useful this activity is content-wise, but I think it does help with recognizing that thing which look linear may not be linear outside the range you’ve measured and the dangers of extrapolation. I’ll think about it more and see what I can find that might be more useful and interesting for the students.