Wednesday, January 28, 2009

3rd Lecture, Brownian motion, energy, conservation of energy

I just uploaded my lecture slides to Scribd (see below) and realized (finally) that Scribd was hacking them up, and not providing the pptx files for download. This is a problem. I probably should just upload them to OWW and provide a link to my students. I had in mind that other people may like to "discover" these, but they're so garbled on Scribd that I think people would be turned off. I did notice that Scribd recognizes images from Flickr and Wikipedia and replaces them with the page they came from. That's pretty cool...although in both cases I noticed, I had attributed the images and provided links, so removing them wasn't appropriate, in my opinion. Any thoughts from people on the best way to share lecture slides? 1/31/09 SJK Note: I got advice from J-C and Cameron to use slideshare, so I've switched to that.

OK, now some comments on today's lecture. First, I'll say that I spent a bunch of time learning names before today's lecture. I think I know about 50 out of 150 students, and within a few lectures, I think I can learn most of them (say 120). The first student who asked a question today, I knew his name, and he said, "wow, that's impressive," and I though to myself, "yes...yes it is." Yes I am tooting my own horn. Not because I'm good at learning names (I stink, actually), but because I think it's a really good thing to do in terms of building a classroom community and I'm achieving it. I think it improves the learning atmosphere and students like it. I think also it vastly increases my enjoyment of teaching. One of my talents is to get real happiness out of students' successes. Knowing their names, and even better, knowing a little about them magnifies this effect greatly.

I have no idea at this point whether students liked today's lecture or any part of the course so far. I had assigned them to read Feynman's lecture about conservation of energy, which I love. I asked them via show of hands who found the reading (like 4 pages) illuminating, and NONE of the >120 people raised their hand! Ouch! That's really good to know, of course. I made the common mistake of putting the students way out of their context of understanding. I love the Feynman piece, but I've been through graduate school in physics. This is many of these students' first science course in college. The irony is that during my first lecture, I led them through that fantastic exercise (Wason selection task), which demonstrates how important context is. Whoops & sorry! I'm not too worried, though, as I am pretty confident that the upcoming topics are going to be pretty interesting and illuminating.

The big demo today was the nose basher. This is the one where there is a bowling ball hung from a hinge on the 20 foot ceiling. The unlucky person (me in this case) holds the bowling ball up against his face, let's it swing down and away, and back again. Of course, it does not bash his face (but please supply youtube videos if you know of other results). But the ball moves remarkably fast when it is mere feet from the face. It's alarming. And quite crowd-pleasing. The demo actually doesn't prove anything per se. But it's so entertaining that I think it's a great backdrop for talking about conservation of energy and energy flow. A student, Brandy, even pointed out that the ball was like an inch from my face, not exactly touching it on the return. This was a great way to point out transfer of energy to the air.

The other demo is the "rattleback," the asymmetric wooden thingy that only likes to spin in one direction. We have a big one that's easy to see. It's a great toy, just fun to observe. And like Nose Basher, it's a good backdrop for discussing energy well as the fact that conservation of energy doesn't let you predict everything about energy flow. I first saw this demo when a famous physicist gave a keynote lecture at Cornell in 1997 or so. He named the rattleback as one of his 7 wonders of the world. Another of his was the "green flash." I don't remember the other five, but they too have probably been solved in the post-wikipedia age :) I remember liking the rattleback, because I had previously noticed it with many telephone handsets (they exhibit the spin / rocking reversal). I tell my physics 102 students what telephone handsets are and explain to them the concept of the "home phone."

Next up on Thursday, we start talking about waves. Two key demos. First is the "wave table." This is such a beautiful demo device. It makes wonderful waves. If I had one of these in my house or office, I would probably spend 5 hours a day waving it. The second is the Ripple Tank applet from Paul Falstad. It's a fantastic applet for demonstrating countless wave phenomena.

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