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J. Perelman
"Entertaining physics". Book 1.
Chapter 4. Rotation. "Perpetual motion machines"


Circle of smooth white cardstock punch in the center of the pointed match; you'll have a chopper in the figure to the left about half natural size. To make it spin on castrandom the end of the match, does not require special skill; it is enough to spin the match between his fingers and quickly drop the chopper on a smooth place.

With this chopper, you can do a very good experience. Before her swirl, apply PA upper side of the mug a few small ink drops. Not allowing them to dry, make the pinwheel to spin. When it stops, look what had happened with the drops: each of them flowed in a spiral line, all these curls together creates a kind of vortex.

As the flow of ink drops on a rotating paper circle.

The similarity with the vortex is not accidental. Talking about inky curls on a cardboard circle? It traces the movement of the ink drops. Drop undergoes the same that a person experiences on a rotating disk “wheel of fun”. Rushing from the center by centrifugal effect, it falls into the disk space, which is more circular speed than the speed of the drops. In these places the circle to slip out from under drops ahead of her. It is as if the drop fell behind the circle, stepped back from the radius. Her life is so distorted, and we see the circle trail curvilinear motion.

The same undergo air flow, diverging from the high-pressure atmosphere (“highs”), or converging to a place of low pressure (“cyclones”). Inky curls - reduced similarity of these giant air vortices.

Entertaining physics J. Perelman


System Orphus


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