Phenomena

Crushing Oobleck

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Oobleck is probably the Internet’s favorite non-Newtonian fluid. People vibrate it, run across it, shoot it, drop it, and even use it to fix potholes. But how does oobleck hold up to a hydraulic press? Fortunately, that’s been covered, too. Oobleck is a mixture of cornstarch and water, and it’s a bit unusual in that it is a shear-thickening material. That means that the faster you try to deform it, the more it will resist that deformation. Knowing this makes the above video’s results make more sense. When they try to crush the balloon full of oobleck, the deformation happens pretty slowly, so the fluid just flows away.

The same thing happens initially with the pot full of oobleck; it overflows much like any other liquid. But as the press pushes deeper, the oobleck gets confined by the pot’s walls and things change. Research has shown that the shear-thickening of oobleck comes from cornstarch particles jamming up in the fluid. By confining the oobleck, the pot and hydraulic press magnify this jamming effect, causing a spurt of semi-solid cornstarch fingers and leaving the press tool thoroughly trapped by the jammed particles. (Video credit: Hydraulic Press Channel)

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