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

THE LEGEND OF THE BOOT IN THE BATH

“Why winter day is short and the night is long, and lot - to the contrary? Day in the winter so short that, like all other things, visible and invisible, from the cold compressed, and the night from phosgene lamps and lanterns is expanding, for warmed”.

Curious reasoning “of the don army retired Sergeant from Chekhov's story makes you smile its apparent incongruity. However, people who laugh at such “scientists” reasoning, themselves often create a theory, perhaps, equally preposterous. Who did not hear or even read about the boot in the bath, oversized on the hot leg though, because the foot while heating has increased in volume”? This famous example has become almost a classic, and yet he is given a totally false explanation.

First of all, the human body temperature in the bath is almost not increased; increased body temperature in the bath does not exceed 1°, lot of 2° (on the shelf). The human body copes with the thermal environment and maintains its own temperature at a certain point.

But when heated at 1-2° C increase in the volume of our body is so insignificant that it cannot be seen when wearing the boots. The expansion coefficient of the hard and soft parts of the human body does not exceed a few desyatitysyachnyj. Therefore, the width of the foot and the thickness of the tibia could increase by only some a hundredth part of an inch. Do the boots are made with a precision of 0.01 cm - thickness of hair?

But of course, the fact is indisputable: the boots are difficult to put on after a bath. The reason, however, is not in thermal expansion, and the rush of blood, the swelling of the outer cover, in the wet the surface of the skin, and similar phenomena that have nothing to do with thermal expansion.

Entertaining physics J. Perelman

 




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