hearting my job

Last week I had a really good period with an exceptional group of students. It was so amazing that it made my entire day, even though the rest of the day wasn't all that great (except for lab, which I always love, and tacos at lunch). I wasn't even all that psyched about the activity beforehand, and it took a ton of time and effort and set that period back a day and a half behind the other periods. However, the grins were well worth it, and I can't wait to do it again.

We started the year with the polar bear game (aside: I learned this at a CIPT workshop years ago, but just did a quick search and found this blog entry. I use it to the same end, although I emphasize how me model physical behavior and then refine our models when they fail to make accurate predictions. I also can't say ice-hole without smirking or worrying that if I say it too quickly it will come out wrong. So I say polar bears around a hole in the ice). Next we we hit the circle lab, which was cool- this was my first year doing it. After that we went to the tried and true Modeling Instruction pendulum. After finishing it and looking at the results, this particular section wasn't convinced and thought that with a larger pendulum we might see results with different bob masses or amplitudes. They were borderline obsessed with figuring this out, and kept asking me how we were going to do it. We had a good discussion about different possibilities and how they could run such an experiment, and I promised to look into using either the gym or the auditorium.

It didn't work out for us to use the gym, so the auditorium it was. I spent one morning scoping out different spots and finally found a place I liked that was directly below the catwalk. I built a seat in the shop one day, and then went in early on the day of the experiment to rig up the pendulum using my climbing gear. The effective length of the rope was somewhere around 30 feet, but since it was constant the students decided that they didn't need to waste time measuring it. We started by figuring out which students were interested in being bobs, and then we chose the order randomly. We used a video camera to capture footage to measure period more accurately with stopwatches, though in hindsight I should have either moved the camera further away or shot high speed video. They measured the mass of each student using a bathroom scale and then they swung back and forth a few times, all starting from the same point.

After we finished changing the mass, we talked about how to change amplitude. I wanted to use a bowling ball, but they decided a person would be more exciting. I responded that it wouldn't be fair to choose just one of them for such an honor, and then they decided that I should do it. I reluctantly agreed, more because I wasn't sure how much the trajectory would change on the longer trials. As the earth rotates the path of a pendulum appears to rotate, though in actuality it's the room that is spinning, not the pendulum. In this case it was worrisome because we were swinging down an aisle whose entrance was bordered by concrete block walls.

To paraphrase one student, "I had fun not only doing the experiment and figuring out if mass made a difference, but also watching you [me]. Your face would change from excited as you swung forward to terrified as you swung back toward the walls. it was priceless." The shot above shows the excited portion of the swing. I never hit the walls, in fact I don't even think I cam close.

We spent a whole period conducting the experiment. Afterwards I tracked all of the students' motion using LoggerPro and figured out the period for each one. The next day in class we watched one of the videos and then I showed them how to track points and determine out period. They were a little bit daunted by the idea of doing that for each video, and I think most were relieved when I explained that I'd already done it (side note: most all of them will do this themselves at some point in the year, so it wasn't a big loss that they didn't all do it). Here is a graph of the data they collected:

I'm not the first person to use a human pendulum, my grandmother showed me an article about a professor at a local college doing the same thing in his lecture. It's a lot of work, but I would heartily recommend it for anyone who is interested. since I have the webbing all set, next year it should be a snap to rig, so long as I don't undo the knots for something else.

Onto other topics... I've been putting together some handouts for kids to use during class as we work through examples. I have had issues with Word and images in the past and have switched to LaTeX. It works well, though it took me a little bit of troubleshooting to get images to show up where I wanted them. I'm going to include a smattering of Context-Rich Problems which I'm hoping to have the kids tackle using the GOAL problem solving technique (adapted as IDEA by colleagues in South America, see here). I also have some Goal-less problems lined up, and of course ranking tasks, can't wait to see how they work.

I had my first student come in for a re-assessment on Friday afternoon. Last year he was always been one to argue about his scores and whether he should have received more points on a problem. He's also been quick to point how that since I count a 4 as proficient on my grading scale, it's basically the same as a 5. The distinction that a 5 shows perfect command of the material while a 4 is just ok seems to be wasted on him. So anyway, I wasn't sure how the re-assessment would go, especially since the request he submitted using my google form wasn't the most reflective I've ever seen (he explained that he looked over his "nots", for one). He took the re-assessment and asked me to tell him how he did. I was looking at it and trying to figure how where he went wrong when he spoke up and said that he was pretty sure that he made a mistake at a certain part. I agreed, and we talked about what could have been done better. He left without arguing and that was that. If this is the effect that SBG can have, I'm all in!