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J. Perelman
"Entertaining physics". Book 2.
Chapter 3. Circular motion


Perhaps you are familiar with dizzying bike trick, sometimes the executable in circuses: a cyclist rides in the loop from the bottom up and describes a complete circle, despite the fact that on top of the circle he has to go upside down. In the arena arrange wooden track in the form of a loop with one or more convolutions, as shown in our drawing. Artist descends on the bike on the inclined part of the loop, then quickly takes off on his steel horse up on its circular part, makes a complete revolution, literally upside down, and safely down to the ground *.

"Damn loop". Bottom left diagram for calculation.

This puzzling Cycling focus seems to spectators top acrobatic art. Puzzled audience puzzled asks himself: what is the mysterious force holding daredevil upside down? Incredulously configured ready to suspect here the cunning, and the trick there is nothing supernatural. He fully explained by the laws of mechanics. Billiard ball, put on this track, would carry out the same with no less success. In high school physics classrooms have miniature "damn loop.

The famous artist and inventor of this trick artist "Mephisto", for testing the strength of the "devil's loop" had a heavy ball, the weight of which was equal to the weight of the artist instead of the bike. The ball was out on the track loop, and if he successfully ran it, the artist has decided to do the loop itself.

The reader, of course, realize that the cause of the strange phenomenon is the same, which explains the well-known experience with rotating bucket. However, the trick is possible but always; you must calculate the height at which the cyclist must start its movement, otherwise the trick will end in disaster.

* "Devil's loop" invented in 1902 at the same time two circus artists - "devil" (Johnson), and "Mephisto" (Noisettes).

Entertaining physics J. Perelman


System Orphus


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