Dear readers, thank you for reading my article in your busy schedule, this is an affirmation of my efforts, but also the motivation to continue to create, I would like to extend my most sincere respect to you, I hope to get one of you"Attention"Thank you!The Janibekov effect, also known as the tennis racket theorem (because it is beautifully illustrated with a tennis racket), was known as early as the 19th century, but it did not get its name until 1985, when Soviet cosmonaut Vladimir Dzhanibekov noticed one of the consequences of the theorem in practice at Salyut 7, however, the Soviet Union then classified this effect. But what is this effect?Why classify it?Let's figure it out.
The tennis racket theorem appears in ordinary mechanics, which uses three moments of inertia around different axes of rotation to describe the rotation of a rigid body. The theorem got its name because it was perfectly proved when we threw a tennis racket into the air.
Any solid has three spindles that rotate. We number these three axes as shown in the image below.
The object rotates stably only when it rotates relative to the first and third axes, but the rotation relative to the second axis becomes unstable and the object constantly changes the direction of this axis, which can be seen from the end of the article. This second axis is sometimes referred to as the intermediate axis.
This effect or theorem applies to all cases where the moment of inertia relation around the axis is as follows: i1 We cannot explain this effect visually without the use of complex mathematics, and this is difficult for most readers to understand, so anyone who wants to know the reasons for it in more detail is welcome to comment, I will try to answer your question in more detail.
In 1985, Vladimir Dzhanibekov of the Salyut 7 space station was working when he unscrewed a wing nut from one of the studs inside the ship, causing the nut to fly freely out of the stud and continue to move by inertia while rotating. After flying in a straight line for about 40 centimeters, she rolled 180 degrees and continued to move in the same direction, but "backward and forward". After a while, she did a similar somersault and returned to her original position.
Vladimir became interested in what would happen if the wing nut (with three axes with significantly different moments of inertia) was completely covered with plasticine and formed into a sphere. Having unscrewed the nut in the same way, Janibekov was sure that nothing had changed in the behavior of the nut, it was still tumbling. When Zanibekov showed the scientific community a video of his experiments, some scientists came up with the idea that the Earth, like a butterfly nut covered with plasticine, would sooner or later turn upside down, which would mean the end of the world. Huge overload during somersaults. Since there is no clear scientific opinion on this issue yet, it was decided to classify the information about the Zanibekov effect for 10 years, believing that this is not intended to spread panic among the less educated population.
Practical application of the Janibekov effect. The Zanibekov effect comes into play when the solid rotates, but once the inside of the solid is filled with liquid, the situation changes radically. Once a liquid-filled object is rotating along any one axis in weightlessness, it will continue to rotate around that axis for some time. However, when a large amount of liquid is dispersed along the inner wall of the body, it will begin to rotate around the axis with the highest moment of inertia, regardless of which axis it originally rotated around. That is, the object will start rotating along an axis with minimal kinetic energy and maximum moment of inertia relative to that axis.
Since the Earth's interior is liquid, and the liquid is distributed in its depths for a long time, the moment of inertia at the time of its rotation has reached its maximum and can never be reversed.
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