OK, “quiz” isn’t really the right word, because I don’t know the right answer. But here’s something weird that I noticed a while ago, and since I needed an excuse to fool around with video a bit, I thought I’d shoot some pictures of it:
Here’s the deal: My cell phone is gently curved on one side. If I put the phone on a table with that side down, it will spin reasonably freely, with very little effort. If I try to spin it fast, though, it very quickly develops a pronounced wobble that damps out the spin very quickly. You can see it in the YouTube video above.
So, the question is: Why does that happen?
(I noticed this while we were interviewing students for a position in the student residential life system that I’m involved with. I think I was starting to annoy the students who were on the interview committee, because I spent the next two hours spinning my phone at different speeds, in different directions, on different surfaces…)
An additional piece of information that might be useful: the effect is much more pronounced on the lab bench where I shot this video than on the lecture-room table where I first noticed it. When I first saw it, the phone would complete a few revolutions before wobbling, and a couple more while wobbling.