The question about stability reminds me of a discussion I had with
my officemate many years ago in grad school. He said one made a turn
on a bicycle by turning the front wheel, and I said I wasn't sure.
Thinking about angular momentum suggested to me that turning the wheel
should cause the bike to fall OUT of the turn. On my way home that
evening, I tried to sit up straight on my bike while I turned the front
wheel. Sure enough, the reaction always caused the bike to lean the
wrong way. If I leaned in the direction I wanted to turn, then the
front wheel would follow. I told this to my officemate the next day,
and he simply declared that I was wrong. I described my reasoning and
my experiment and suggested he try the experiment himself. (It's amazing
how many physicists seem to prefer Aristotelian reasoning to simple
experiments sometimes...) Anyway, he came in the next day and told me
he had tried my experiment and said "I nearly killed myself!'.
Apparently he had tried to turn the front wheel while moving fairly
quickly and nearly lost control of the bike when it leaned the wrong
way.
Steve Luzader
Frostburg State University
sluzader@fre.fsu.umd.edu