Oobleck on a Speaker by Darren Seaney
3rd Place - Contrived Category
School: Glenbard West
Teacher: Bruce Medic
This photograph shows a non-Newtonian fluid on a vibrating speaker. The fluid is oobleck, a suspension of cornstarch in water. Oobleck is a non-Newtonian fluid because its viscosity is affected by pressure. Specifically, it is a dilatant fluid, meaning that as pressure is increased on the material, its viscosity increases. This happens because the sugars from the corn starch are not able to move freely past each other when pressure is applied, and it behaves with some characteristics of a solid rather than a free flowing aqueous solution. Because of the pressure applied by the speaker to the oobleck, the oobleck moves, but is not thrown off the speaker as would be expected with the same experiment with only water, for example. The speaker applies pressure by striking and retracting extremely quickly, so the pressure applied to the ooblick is constantly changing. If a higher frequency had been used, the oobleck would have behaved more like a solid, and clumped together. However, it was determined that about 30 hertz was the sweet spot for this suspension, and the oobleck started to change back to a liquid before the stereo struck again, as seen by the plateaus and columns in the photograph.