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J. Perelman
"Entertaining physics". Book 1.
Chapter 6. Thermal phenomena

MYSTERY SPINNER

Of thin tissue paper, cut a rectangle. Fold it on the middle line and straighten again: you will know where the center of gravity of your body. We now put the paper on the edge of the protruding needle so that the needle propped her just at this point.

The paper will remain in equilibrium: it is supported at the center of gravity. But from the slightest breath of wind it will start to rotate on the edge.

While the device does not detect anything mysterious. But move your hand to him, as shown in the figure; gently put to paper was not swept away by the current of air. You will see a strange thing: the paper will start to rotate, slowly at first, then faster. Slide the arm - rotation stops. Zoom - start again.


Why test spin?

This mysterious rotation at one time - in the seventies of last century gave many a reason to think that our body has some supernatural properties. Lovers of mystical found in this experiment the confirmation of his vague teachings about coming from the human body is a mysterious force. Meanwhile, the reason is quite natural and very simple: the air heated from below your hand rises up and, pressing on the paper causes it to rotate, like all famous spiral “the snake” over the lamp, because bending the piece of paper you gave her the parts easy slope.

A careful observer may notice that describes the turntable rotates in one direction - from the wrist, along the palm to the fingers. This can be explained by the temperature difference of the mentioned parts of the arms, the ends of the fingers are always cooler than the palm of his hand; so near the palm is formed over a strong upward current of air which strikes the paper is stronger than the current generated by the warmth of the fingers [You may also notice that when the fever and generally at elevated temperature, the turntable moves much faster. This illuminating device, once many vexations, was in his time devoted even a small physical-physiological study, reported in the Moscow medical society in 1876 (N. P. Nechaev, rotation of the light bodies by the action of heat hand)].

Entertaining physics J. Perelman

 




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