OK, it’s not really a full post-mortem, because I haven’t graded the final exams yet, but I wouldn’t tell you about those, anyway. Still, I wanted to take a moment to reflect on the past term, which was my first teaching introductory mechanics on the Matter & Interactions curriculum.
On the whole, I continue to like the approach. I like the way that the book focuses on the major physical principles– the Momentum Principle, the Energy Principle, the Angular Momentum Principle– because those are the real take-away message from introductory physics. I also thing it’s good that the class doesn’t look like high school physics all over again, but forces students who have had a good high school class to take another look at the same material, rather than just falling back on what they’ve done before.
Of course, it’s not all flowers and happy bunnies…
As much as I like the focus on big principles, I found that the text was awfully short on the sort of straightforward problems and examples that students need to practice on. I used WebAssign to assign homework nightly, but there were times when it was awfully difficult to find useful problems. There are great, detailed, realistic end-of-chapter problems, but it’s a big jump from the discussion in the text to those problems. some sections covering important example problems had no exercises at all, while other sections had tons of examples, on topics that were too curriculum-specific to be generally useful.
Chapter 9, on collisions, was particularly bad in this regard. There is really only one general problem about elastic collisions, asking students to find a general solution for an elastic collision with a stationary target. That’s a hard problem for them, even when they get some problems with actual numbers to practice on; without detailed examples, it’s pretty hopeless. And I would say that the techniques involved in doing elastic collision problems are really crucial for future physics classes– the whole idea of getting constraints from multiple physical principles, and solving systems of equations to find multiple unknowns is key to a lot of what comes later.
Some of the other omissions are more of a mixed bag. There’s relatively little time spent doing vector problems using magnitudes and angles, which isn’t great, but then again, I can’t say I missed the iconic block-on-an-inclined-plane problems all that much. Likewise the endless variants of projectile motion.
The first time through a new curriculum is always a little rocky (I’m glad I have tenure…), and I think the next time I teach it will go a little more smoothly, now that I know what to expect. I’ll go back into old exam questions and Halliday and Resnick to find practice problems to fill in the gaps, and I’ll know where I need to spend more time on in-class examples.
Some other issues with this edition of the course have less to do with the book than with local constraints. We teach on a trimester system, but the engineering students who are the main audience for the class only take two terms of physics, rather than a full year. They have certain expectations of the classes, so we’re forced to squeeze the curriculum in ways that the authors never intended– we skip Chapter 7 (on quantization) completely, and rush through Chapters 8 and 9 to end with Chapter 10, on angular momentum. This has the unfortunate effect of putting the hardest material of the class in the last week of class, just at the point where everybody’s nerves are completely shot. Were we working with a semester system, Chapter 10 would come with three weeks to go, and there would be time for students to get more comfortable with angular momentum, and we’d end with the less intimidating material on basic thermodynamics.
I’m not entirely happy with the way this term went, but a lot of that was just the shakedown cruise effect. If I teach this class again next year, I expect things will go more smoothly; in fact, I look forward to taking another pass through this material. And given how sick I was of intro mechanics before this year, that’s really saying something.