I’ve gotten a little behind on these updates. What can I say, the Jackson E&M problem sets are really starting to get hard. Plus, this past week, I had to grade 217 quiz problems from the first quiz. But there’s no rest for the weary in this business…
Don’t forget the latest installment of Adventures of the Learning Assistant over at Morning Coffee Physics.
The discussion session for week three was a group quiz. The students, working in the same groups that they’ve been in for the past two weeks, work on a problem that will count as the first question of their quiz, which they finish in class the next day. It’s nice for the TAs, since we don’t have to answer any questions or help the students like we normally do, so we can just relax (or work on problems from Jackson).
The group problem was a pretty straightforward problem in kinematics, and most of the groups did pretty well. I have to admit feeling somewhat of a sense of pride as I eavesdropped on the students while they were working. The group problem solving and approach to physics problems have come a long way in a fairly brief time.
I began the lab in week three by handing out a sheet describing my general expectations for lab reports and going over it a little bit. I then strongly hinted that the lab that day would be the lab that they would be writing up for the first paper, so they should do a good job on it. In general, they’re not supposed to know ahead of time which lab they’re writing up, so that they’ll be forced to take good data for every lab they do, but I figured it would be helpful to give them a little break on the first one.
The lab itself was on the normal force and frictional force, with the standard block-sliding-down-ramp setup. Unfortunately, this lab came a little earlier than the topic of friction in the lecture, which always throws students off, even if, as a TA, you cover the relevant issues in the pre-lab discussion.
I haven’t graded many of the reports yet, so we’ll see how that goes. The first lab report is always going to be pretty bad, as the students try to feel out my expectations and develop an understanding for what sort of things should go into a lab report. That’s why they get to re-write the first one. Uncertain Principles has some interesting discussion about the role of lab reports in undergrad labs that you should check out.
Going into the discussion this week, I didn’t think the problem would be too bad, but the students had a lot more trouble than I expected. It’s a pretty commonly used problem: the “fuzzy dice” problem. Essentially, the problem reads “If fuzzy dice hanging from the rearview mirror of a car make a certain angle with the vertical, what is the car’s acceleration?”
Looking back at it, it really does contain a fair number of concepts; breaking forces into components, equilibrium in one direction, unbalanced force leading to acceleration in the other dimension. Now, extracting these physics concepts from the context of the problem is not trivial for beginning physics students, but I figured once I walked them through that challenge on a group-by-group basis, they’d be home free. It didn’t exactly work out that way, and for several groups, even after I thought I had gotten them on the right track, still needed me to basically walk through the setup step by step.
I don’t know that I necessarily did a good job of explaining the problem, even at the end at the chalkboard. I’ve seen these problems so many times that a lot of things seem intuitive that are not at all obvious to my students. Also, since this is my first or second time trying to teach these concepts, I don’t always have a good grasp of which “obvious” steps will be the most confusing to my students.
Labs in week four were nothing remarkable. We had a simple projectile motion analysis using the video software that was more of an investigation than an experiment. It was more of “look, balls really do follow the projectile motion equations from the book!” type of lab.
The other problem was an equilibrium problem. This one was useful because it was a good setting for doing percent error between a measurement and a prediction made from an equation we (I) derived in pre-lab discussion.