The Bizarre Behavior of Rotating Bodies

Spinning objects have strange instabilities known as The Dzhanibekov Effect or Tennis Racket Theorem - this video offers an intuitive explanation.

References:

The Twisting Tennis Racket

Janibekov’s effect and the laws of mechanics

Tumbling Asteroids

The Exact Computation of the Free Rigid Body Motion and Its Use in Splitting Methods
SIAM J. Sci. Comput., 30(4), 2084–2112
E. Celledoni, F. Fassò, N. Säfström, and A. Zanna

Animations by Ivy Tello and Isaac Frame

Special thanks to people who discussed this video with me:
Astronaut Don Pettit
Henry Reich of MinutePhysics
Grant Sanderson of 3blue1brown
Vert Dider (Russian YouTube channel)

Below is a further discussion by Henry Reich that I think helps summarize why axes 1 and 3 are generally stable while axis 2 is not:

In general, you might imagine that because the object can rotate in a bunch of different directions, the components of energy and momentum could be free to change while keeping the total momentum constant.

However, in the case of axis 1, the kinetic energy is the highest possible for a given angular momentum, and in the case of axis 3, the kinetic energy is the lowest possible for a given angular momentum (which can be easily shown from conservation of energy and momentum equations, and is also fairly intuitive from the fact that kinetic energy is proportional to velocity squared, while momentum is proportional to velocity - so in the case of axis 1, the smaller masses will have to be spinning faster for a given momentum, and will thus have more energy, and vice versa for axis 3 where all the masses are spinning: the energy will be lowest). In fact, this is a strict inequality - if the energy is highest possible, there are no other possible combinations of momenta other than L2=L3=0, and vice versa for if the energy is the lowest possible.

Because of this, in the case of axis 1 the energy is so high that there simply aren't any other possible combinations of angular momentum components L1, L2 and L3 - the object would have to lose energy in order to spin differently. And in the case of axis 3, the energy is so low that there likewise is no way for the object to be rotating other than purely around axis 3 - it would have to gain energy. However, there's no such constraint for axis 2, since the energy is somewhere in between the min and max possible. This, together with the centrifugal effects, means that the components of momentum DO change.

[joedaly]

As a carpenter for over fifty years I've recognized this behavior with flipping of a hammer because I early on decided to teach myself to juggle hammers. I tried to prevent the twist-flip with absolutely no success. It became clear there was more stability in working with the flip instead of against it. This explanation is such a relief! I thought it was a personal curse. Now I realize hammers are the perfect object to demonstrate this motion because they, unlike tennis rackets, have no symmetry about any axis!

[rvamark]

I was a dynamicist in the aerospace industry for 43 years, and THAT is the BEST plain text explanation of this behavior I have ever seen! Fantastic!

[false]

This is the content I subscribed for. Well done!

[alexanderkurz]

I love how you manage to pack so much into one video, physics, history, personal interest stories, tangents to pursue further ... this is how I would like to teach and I know how hard it is to do

[llll-lkmm]

This explaination is beautiful when you're actually learning this stuff in school... keeps me wanting to know more. Thanks Veritasium!!!

[qfmarsh]

As a kid, I would frequently watch my dad flipping the TV remote control in his hand and studying the inevitable half-turn in its flight pattern. He concluded that his wrist was subtly imparting spin.

If he were alive today, his mind would probably be blown watching this video.

[davidking]

I've been flipping tennis rackets for years and never been able to get my head around this effect. Incredible.

[tonyfourpaws]

I got in trouble at work today because I was tossing various objects and watching the flip. I tried to explain it to the boss but he wasn't having it. He fired me. Now I have more time to watch your videos!

[alvirahesc]

"Babe, come over, im home alone"

"No, babe, Im solvin a centuries old math problem."

[andrewchapman]

Video: contains the phrase "prove Feynman wrong"


Also video: doesn't use this phrase as clickbait.


I salute you.

[EtzEchad]

"The goal of this video is to prove Feynman wrong."

You have high ambitions, young man!

[youtubeboi]

I have a feeling that when Feynman replied "No" to the question, it was because he considered even this "intuitive" explanation, not that intuitive for most non-physicists/engineers.

[kodycook]

I'm a carpenter and I'm constantly flipping my hammer while I'm not busy. I've wondered for the past 10 years (I became a carpenter in 2010) why is it the head and claws of my hammer flip flop when I flip my hammer head over handle. I thank you for this video!! I suffer from ADD/ADHD and I find myself pondering this very often (driving myself nuts over it). Thanks again for the answers!!!!

[DanielRenardAnimation]

*Russian Cosmonaut spins a wingnut in space:* _"TELL NO ONE OF THIS!"_

[johnnyroman]

This phenomenon fascinated me as a 10 year old since I’ve been obsessed with skateboarding, (specifically flip tricks); and although I could not explain it, it was what first got me interested in physics.

[shawn]

I always assumed this happened because I was adding spin without realizing it. The theory of a rotating object trying to minimize its kinetic energy actually makes a lot of sense.

[Koutentogiwrghs]

A colleague pointed me to this great video! I was fascinated to find that it also contained two additional facts about the great condensed matter physicists of the past century.
1) If you claim that any physical concept is not in the Landau-Lifshitz books, most probably you have not looked for it as carefully as you should.
2) It is really tough to beat Feynman's physical intuition on anything, even if he thought about it for less than half a minute.

[billdecat]

So the next time someone calls me "a flipping wingnut" I'll know why.

[aliasghar_mech_eng]

How beautiful you explained one of the most counterintiuitive physics problems in an intuitive way.

[milosveselinovic]

I’m just happy there is a scientific explanation for that