A spool of thread is placed on a table… What does it revolve around? Around its axis?
If the reel is placed on a table, there may be surprises, therotation axis is not what you think!
A coil of thread is placed on a table (left, side view, right, front view). We pull on the wire. How will the reel move?
Answer :
It depends on the axis along which the coil is pulled! Up to a certain inclination, the reel will follow whoever pulls it, beyond that, it will be the opposite.
The result may seem paradoxical because the axis of rotation corresponds to the point of contact I with the table and not to the center of the circle. In case 1, the coil will go to the right. If we straighten the wire coming out of the coil, to obtain case 2, it is the opposite. The limit position IJ is where the wire comes out in line with the point of contact between the coil and the table.
Learn more about Hervé Lehning
Normalien and agrégation in mathematics, Hervé Lehning taught his discipline for a good forty years. Mad about cryptography, member of the Association of encryption and information security reservists, he has in particular pierced the secrets of Henri II’s cipher box.
Also to discover: The universe of secret codes from Antiquity to the Internet published in 2012 by Ixelles.
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