
Tennis racket theorem – Wikipedia - rbanffy
https://en.wikipedia.org/wiki/Tennis_racket_theorem
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castratikron
Classical mechanics was my favorite course in college. It doesn't get enough
fame (everyone always wants to talk about quantum mechanics, because it's
"weird").

Check this fun problem out: [http://www-groups.dcs.st-
and.ac.uk/history/HistTopics/Brachi...](http://www-groups.dcs.st-
and.ac.uk/history/HistTopics/Brachistochrone.html)

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pavel_lishin
I remember seeing a list of unsolved problems in Newtonian physics; some
seemed really interesting, involving infinitely-fast projectiles that can slow
down to a stop in non-infinite time (implying the reverse ought to also be
true).

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kingbirdy
You can demonstrate this very easily with your phone (all directions given
assuming the phone is facing you, oriented vertically): rotating it cw/ccw
will be stable (you're on the shortest axis, only the depth of your phone,
probably a few mm), flipping it left-to-right will be stable (you're on the
longest axis, the height of your phone, probably ~5"), but flipping it top-to-
bottom will result in an uncontrollable spin, as that's the middle axis (the
width of your phone , probably 2-3")

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mannykannot
This tumbling around a different axis after starting a rotation around another
reminded me of something else - the problem of inertia coupling that caused
several crashes of early supersonic airplanes. I would be interested to know
if they are related.

