Recent content by AndyRuina

There are more videos, photos and a paper describing the experiment and concepts. Google ruina falling chains. Or go here: http://ruina.tam.cornell.edu/research/topics/fallingchains/index.html.

Angle is not critical, a pretty big range of angles would work, maybe 5 - 30 degrees

About the angle, a dfinitie answer. Not calculated. No fiddling. A random guess and that was that. Probably anything between about 5 degrees and 30 degrees would work. At least that's a guess about what would work.

Definitive answer about the choice of angle. A single random guess, no calculation and no fiddling.

The light switch analogy works for me here. It is like throwing a heavy light switch. When it collides at the other side, and doesn't bounce, it doesn't come back. The initial throw has some energy and some angular momentum. As you note, the angular momentum can't get lost without air...

Hi A.T.: I got a message saying you invited me to look at this. I don't know who you are? Last week I visited two physics departments and I swear I saw about 5 of these on various office shelves. I have held one but not looked closely at the (clever) mechanism. But clearly it is bi-stable...

I think most of the posts above are a bit off topic. The second one by Tumbling Dice is on topic. I think it is misleading to get into circular motion, centripetal forces and all that. The issue is in the mechanics of wheels. A wheel is generally idealized as light, compared to a car, and...

Infinite friction A few comments and clarifications from a self-declared relative expert (My PhD was about friction, I have written a textbook about mechanics): 1) When proposing or modeling problems where there could conceivably be slip, people often say "assume infinite friction". This...

Hi: Andy Ruina here. I am the fat bald bearded guy with a lisp in the 7 minute video that A.T. posted. A. Reading the whole discussion here I think one gets a sense of a consensus that I agree with. 1) Bicycles are balanced by steering. 2) Moving bicycles can balance...