When a Russian Astronaut aboard their space station spun a wingnut off of a bolt in zero gravity, something very strange happened.
The bolt continued to spin weightlessly for a few seconds... and then it spontaneously flipped over, 180 degrees, and continued to spin. It then flipped over again on its own, and continued to spin... and spun, and spun, continuously flipping over every few seconds.
It was so strange looking, and unexpected, the Russians kept the (totally repeatable) observation a secret for 10 years.
Little did they know, the Americans already knew all about this particular phenomenon.. It's called "The Tennis Racket Theorem".. otherwise known as the "Intermediate Axis Theorem". It goes like this...
Any body with mass that has 3 different moments of inertia (a maximum, a minimum, and an intermediate) will behave this way...
If you rotate the body around either axis of it's maximum or minimum inertia, then nothing special happens. It spins as expected.
If you attempt to rotate the body around its intermediate axis, the body will also spontaneously rotate around it's axis of minimum inertia.
This is easily demonstrated with a tennis racket;
If you hold the racket out in front of you, like you were about to return a serve, and spin it in the air with a twist of the wrist, you will be spinning it along it's axis of minimum inertia.. and it will just spin as expected. Likewise, if you are holding the racket out in front of you, and spin it like a platter, with one face pointing upward and the other pointing downward at all times, then you will be spinning it along it's axis of maximum inertia. Again, nothing special happens.
BUT... try and "flip" it... spin it along it's intermediate axis, like you were tossing the racket into the air and catching it again after the handle rotates away and back into your hand.. something odd happens... it "twists"... or rather, also rotates along its minimum axis... no matter what you do or how you attempt to rotate it.
There is no stopping it. It is impossible to flip a tennis racket without it also spontaneously "twisting" in the air.
Can anybody:
a) explain why this happens and how one could predict when it flips over
b) propose a novel way to exploit this behavior for Good(TM)? Or identify where this has been used in engineering or whatever to solve a problem...
The bolt continued to spin weightlessly for a few seconds... and then it spontaneously flipped over, 180 degrees, and continued to spin. It then flipped over again on its own, and continued to spin... and spun, and spun, continuously flipping over every few seconds.
It was so strange looking, and unexpected, the Russians kept the (totally repeatable) observation a secret for 10 years.
Little did they know, the Americans already knew all about this particular phenomenon.. It's called "The Tennis Racket Theorem".. otherwise known as the "Intermediate Axis Theorem". It goes like this...
Any body with mass that has 3 different moments of inertia (a maximum, a minimum, and an intermediate) will behave this way...
If you rotate the body around either axis of it's maximum or minimum inertia, then nothing special happens. It spins as expected.
If you attempt to rotate the body around its intermediate axis, the body will also spontaneously rotate around it's axis of minimum inertia.
This is easily demonstrated with a tennis racket;
If you hold the racket out in front of you, like you were about to return a serve, and spin it in the air with a twist of the wrist, you will be spinning it along it's axis of minimum inertia.. and it will just spin as expected. Likewise, if you are holding the racket out in front of you, and spin it like a platter, with one face pointing upward and the other pointing downward at all times, then you will be spinning it along it's axis of maximum inertia. Again, nothing special happens.
BUT... try and "flip" it... spin it along it's intermediate axis, like you were tossing the racket into the air and catching it again after the handle rotates away and back into your hand.. something odd happens... it "twists"... or rather, also rotates along its minimum axis... no matter what you do or how you attempt to rotate it.
There is no stopping it. It is impossible to flip a tennis racket without it also spontaneously "twisting" in the air.
Can anybody:
a) explain why this happens and how one could predict when it flips over
b) propose a novel way to exploit this behavior for Good(TM)? Or identify where this has been used in engineering or whatever to solve a problem...