[Grand Illusions] Intermediate Axis Spinning Top

🎯 Загружено автоматически через бота: 🚫 Оригинал видео: 📺 Данное видео принадлежит каналу «Grand Illusions» (@grandillusions). Оно представлено в нашем сообществе исключительно в информационных, научных, образовательных или культурных целях. Наше сообщество не утверждает никаких прав на данное видео. Пожалуйста, поддержите автора, посетив его оригинальный канал. ✉️ Если у вас есть претензии к авторским правам на данное видео, пожалуйста, свяжитесь с нами по почте support@, и мы немедленно удалим его. 📃 Оригинальное описание: Sign up for the free Grand Illusions newsletter, at _______________________________________________________________________ This deceptively simple little spinning top exhibits some very unusual behaviour. A rectangular wooden block forms the main part of the top, and each of the three sides is of a different length. This fact is important and is the key to the way this top behaves. You can spin the top on the red axis, on the green axis, or on the black axis. If you spin it on the green axis it will continue to spin nicely for a reasonable length of time. The same happens when you spin it on the black axis. However, if you hold it so that the red axis is vertical and you spin it around that axis, something remarkable happens. Almost immediately it tumbles and turns and ends up in a stable rotation around the black axis! This fascinating behaviour is related to the so called ‘intermediate axis theorem’ or ‘tennis racket theorem’ or the ‘Dzhanibekov effect’. The physics behind this effect has been known since the early 19th century. However the Soviet cosmonaut Vladimir Dzhanibekov observed one of the logical consequences of the theory whilst in space in 1985. The wooden block has three principal axes of inertia. These are the three coloured axes. The green axis has the smallest moment of inertia, and it is the axis around which it is the easiest to set the top spinning. The black axis has the maximum moment of inertia – it is hardest to spin the top around this axis. Spinning the top around either of these two axes results in a stable rotation, and it can be shown that the black axis (the one with the largest moment of inertia) gives the most stable rotation. The red axis is called the ‘intermediate axis’, because its moment of inertia is larger than that of the green axis, but smaller than that of the black axis. Rotation about the intermediate axis is unstable. When you spin the top around the red axis, i.e. the intermediate axis, it cannot hold the top spinning in a stable manner, and the top quickly settles into a spin around the most stable axis, i.e. the black one. To make the effect even more dramatic you can attach some of the supplied coloured stickers to the two largest faces of the top (the faces that will either be facing up or down when you spin the top on the black axis). When you then spin the top on the red axis and it switches to the black axis, you will suddenly see colour appear, as the stickers are now on the top face. There is a further interesting effect, which is shown when you hold the top in your fingers, spin it around one of the axes, and let go. Best to do this over a soft surface, so there is no damage when the top hits the ground. The effect happens quite fast, and it can be helpful to film it and then slow the film down. Basically, if you spin the top on the black or the green axis, it simply falls down, while continuing to spin on that initial axis. However, if you spin the top on the red axis and then let it fall, it will rotate 180 degrees in the air so it is still spinning on the red axis but is now pointing in the opposite direction – this is why we have marked one end of the red axis with a single band of colour, and the other end of the axis with two bands. The top will then rotate again, so that it is still spinning on the red axis but now pointing in the original direction again. It will do this a number of times, depending on how far it has to fall. In space, an object will continue reversing direction over and over again for a long time! There are spectacular videos on YouTube, especially if the experiments are performed in weightless conditions, e.g. by astronauts on the International Space Station – search for ‘Dzhanibekov effect space’. See and also We are grateful to Nándor Bokor, from the Physics Department of Budapest University of Technology and Economics, who invented this top, and brought it to our attention. _______________________________________________ MUSIC COPYRIGHT The music used in this video is a track called Unfamiliar City, which is Track 6 on a CD called Ambient Textures (AK 107) from . AKM produce discs which once you have bought the disc allow the music to be used without any further royalty payments.