by Toby J. Swaford, K-12 Education Coordinator
One of the Museum’s popular offerings at this last weekend’s New West Fest featured a non-Newtonian fluid (in the form of cornstarch dissolved in water) and an old subwoofer. While this may seem like an unlikely combination, the two work rather well together in a wacky mix of kitchen chemistry and the science of sound.
First off, this particular non-Newtonian fluid acts like a solid when pressure is applied to it; you can even roll it into a ball as long as you keep the pressure up. Think of the particles of corn starch as people on a crowded sidewalk – if you move slowly through the crowd you may be able to flow between the people and move fluidly. On the other hand, if you simply try to run straight through the crowd you will quickly meet with resistance. The same holds true when dealing with the cornstarch and water mixture, you can easily push your finger tip into it with little resistance; however, if you tried to slap your whole hand down on the surface you would discover that it acts more like a solid than a liquid. This is due to the sudden pressure that your hand applies to the substance.
Sound waves can also produce pressure, especially in the lower bass registers, with some interesting effects on our non-Newtonian fluid. Check out the video for an example of what I’m talking about.