July 19, 2012 20:01
Pour enough of the cornstarch into the pool — and you can walk on the surface of water. Scientists were able to uncover the secret of the trick at a party with Youtube.
If you hit the liquid leg, starch particles are suspended in the water, coming together just as the snow plow is going around. This seal forms a heavy site, which can repel with the same falling down pressure, which is concentrated at the tip of the high stiletto heels, report scientists July 12 in the journal "Nature", informs «WordScience.org».
"If you try to hit the suspension, you could break your wrist," said Scott Veytukeytis, a physicist at the University of Chicago, who began studying the viscous material after watching video of people running around on the surface of the liquid.
Water, adding to the cornstarch in equal or greater amounts, due to their duplicity, for a long time been the main product demonstrations at science fairs. It was called "non-Newtonian fluid", as it does not behave like an ordinary liquid.
If you gently put it in her hand, it is quite enough to fit in exactly with little resistance. But if you're really on a hit, get at least a strong back.
To understand how the strength, the researchers hit with great force mix metal rod and observe the effects. In previous experiments, they rubbed the material between two plates — this is a common technique for determining the properties of liquids, but it separates the liquid into two parts, rather than to the direct effect.
X-rays showed an opaque substance, the material was moving under the surface. Modeling based on the information received suggests that the initial impact to squeeze water out of the space between the particles of starch. Then he played a role friction between particles. They are grouped in an extended front, which acted as a solid, repelling effect of the rod.
"The results of the experiment I was not really surprised," — said Daniel Bonn, a physicist at the University of Amsterdam, who proposed a mechanism of events after the experiments, including shots of bullets in the starch slurry. "But the experiment was interesting, because they were able to look inside the starch as it is sealed."
And Bonn, and Veytukeytis hope that understanding the mechanism of the behavior of starch will help other researchers who are trying to create a "liquid" by absorbing Kevlar vest in such suspensions. But they both warn that what is happening in some suspensions may not occur in others.
Despite decades of research, no one has understood why cornstarch thickened with anxiety, while the shifting sands and ketchup contrary resolve, though in all cases dealing with particles that are suspended in liquids.
Aluminum rod, beating the mixture of cornstarch and water can not penetrate into the mix, because the particles are compressed in it, like snow compacted snow thrower.