Continuing our American/Canadian duality, see Morning Coffee Physics’ Adventures of the Learning Assistant Week 2.
Also, check out Uncertain Principles’ latest installment of his modern physics course report.
Life in the Lab
This week, the second week of classes, was the first week of real labs, consisting of two fairly canonical problems: the falling ball and the cart rolling down a ramp.
Before I got to my first lab, all the TAs for the introductory lab received an email telling us that new video analysis software had been installed on the lab computers. The old software certainly had its problems; the on-screen instructions were often confusing, and they had a “feature” that made it impossible to go back a step without restarting the lab. The new software was supposed to fix these problems, among others.
However, the timing of the announcement was not great. We had spent time the previous week getting the students acquainted with the old software (we had no idea it was about to be replaced), and the announcement came in the middle of the week, when I would have no time to try out the software before my students did. However, on the advice of a fellow TA, I decided to have the students jump into the new software feet first. The transition went fairly well, as most of their experience with the old program transferred quite easily. I did spend a lot of time answering computer-related questions, more time than I spent on physics-related questions, but that’s just how the first couple of weeks go.
Each lab session begins with a discussion of the assigned warm-up questions from the lab manual. All of the students had trouble with the warm-up questions this week because the lab is currently ahead of the lecture in terms of the concepts covered. The students have covered kinematics but not Newton’s laws or forces. Also, the lab manuals like to bring in conservation of energy to problems that I think are understood more clearly in terms of forces. And besides, energy is even farther off into the future of the lecture.
However, I was able to get a fairly good discussion about kinematics out of the problems. We discussed the position vs. time and velocity vs. time graphs for each problem, focusing on the shapes of the graphs (quadratic vs. linear), and the relationships between the two (derivative). Because some groups set up their coordinates with up as positive, while others chose down as positive, I was able to make an important point about the importance of defining your axes and being consistent with minus signs. Finally, we brought out the key point that the shapes of the graphs are the same for the ball and for the cart on a ramp, because they have the common feature of a constant acceleration.
I think the discussion went very well this week. The problem was a pretty simple kinematics question, once you extract the meat of the problem from the words of the problem statement (harder for some students than for others). Most of the groups finished the problem much faster than intended, but fortunately I had thought up an interesting extension question to keep them occupied for a little longer.
I think that most of the groups are getting the hang of working in the group setting, which is encouraging, because the next discussion is the group problem for the quiz.