Эффект Джанибекова The Effect Dzhanibekova
Why Physics Stack Exchange recommends it
Physics Stack Exchange answerers and commenters link it as a visual example of the Dzhanibekov effect and the unstable rotation about an object's intermediate axis.
Recommended by 1 people across 1 different months, 2011 to 2020.
What it is
A 16-second clip showing the Dzhanibekov effect, also called the tennis racket theorem, in which a spinning object with three distinct moments of inertia flips over periodically while spinning in weightlessness. It is a short uploaded demonstration with no narration or explanation.
Cited in 1 Wikipedia article, including Tennis racket theorem.
What people said
Recommends Dale · 2013-06 · Physics Stack Exchange · on “Stability of rotation of a rectangular prism”
The instability inherent in the medium length axis or $\prod_2 $ as shown above is discussed in detail in Marsden and Ratiu [LINK] , which is where the image is from. The unstable homoclinic orbit that connect the two unstable points have intersting features. Not only are they interesting because of the chaotic solutions via the Poincare-Melnikov method that can be obtained in various perturbed systems (ref), but already, the orbit itself is interesting since a rigid body tossed about its middle axis will undergo an interesting (and unexpected) half twist when the opposite saddle point is reached even though the rotation axis has returned to where it was. The interesting half-twist is best s
Cites Hans de Vries · 2011-11 · Physics Stack Exchange · on “Why does this object periodically turn itself?”
It's a classical mechanics effect for sure although a really interesting one. Following links on "Dzhanibekov effect" one gets at Marsden and Ratiu's "Introduction to Mechanics and Symmetry" [LINK] Chapter 15 Section 15.9 "Rigid Body Stability" treating this with use of the Casimir functions. From remark 1: A rigid body tossed about its middle axis will undergo an interesting half twist when the opposite saddle point is reached . Here is another and more profound example under weightless conditions. [this video] This seems to be a home experiment where a guy throws the spinning object upwards. [LINK] And this seems to be a computer simulation. [LINK] There is a related unstable orbit effect which
Cites Suzan Cioc · 2012-12 · Physics Stack Exchange · on “Two axes for rotational motion”
Rotation is geometrically possible only over one axis. This axis can change in time, but at each instant it will be one. This is geometrical property of 3d space. Angular momentum axis does not coincide with rotation axis. Generally, rotation axis do precess around angular momentum axis. Here is the example of rotating body whose angular momentum is absolutely constant, but rotation axis does vary: [this video]
Cites ren · 2015-05 · Physics Stack Exchange · on “Janibekov Effect”
Recently I've learned about Janibekov effect [this video] , which looks like magic. What's the explanation behind it? I remeber from school that if no force is applied then object should keep still or continue going as it did, what is the force in this case?
Cites Nikolaj-K · 2015-05 · Physics Stack Exchange · on “Is there a rotational equivalent to newtons laws?”
@CuriousOne: You say "not true", but I feel you can bend the meaning of the words in the formulation to make it fit. It might be worth it to point out that there are funky things like the tennis racket theorem [this video] . That's why I said we must keep in mind that however we (re-)formulate the statements here, it must correspond to some truths in classical mechanics. The interesting question would be that if we take the stance to take the resulting statements as axioms, how much must we add to get Newton back. PS, Ullah: I'd not trouble myself with Newton too much.
Cites Bob Spacklspyer · 2020-02 · Physics Stack Exchange · on “Why does my tea periodically alternate its rotational speed after stirring? (Link to video below)”
Possibly the Dzhanibekov effect in a fluid: [this video] Perhaps a more controlled experiment where motions outside the surface plane are minimized could be created to prevent the occurrence of the effect, but even then, I suspect the effect is unavoidable due to irregularities created in a liquid by the spinning motion itself that would cause the moment to move away from the exact center.