Euler's Disk Spinning Desk Toy amazes and teaches as it spins on your desktop. Here's the science behind how it works: if you spin a coin on a tabletop, it loses energy and tips toward the surface. Wait long enough and the coin begins to roll on its rim, wobbling faster and faster and faster. Toward the end, the coin generates a characteristic rattling sound of rapidly increasing frequency until it suddenly stops with a distinctive shudder.
Mathematician H. Keith Moffatt of the Isaac Newton Institute for Mathematical Sciences in Cambridge, England, now offers an explanation of why this motion ends so abruptly instead of lingering as the coin keeps on rolling faster. The culprit is the thin layer of air trapped between the tipping coin and the table, he reports in the NATURE magazine. As its tilt becomes more pronounced, the rolling coin squeezes and swirls the air beneath. The flowing air takes up energy, tipping the coin even closer to the surface. At some point, the coin's edge finally loses its grip on the table and falls flat. Similar science applications include the common Frisbee.
The larger and heavier the disk, the more dramatic is the effect, Moffatt notes. Such long-lived behavior can be observed in our Euler's Disk Spinning Desk Toy that has a rounded edge to help keep it in motion for remarkably long periods. To see its action, set the 3" diameter 1/2" thick, chrome-plated steel disk on top of the concave mirror and give it a spin. The concave shape makes the disk accelerate while the mirror makes it appear that it will never stop -- its appearance changes and it begins to generate a mysterious hum. Comes with different holographic film pieces to customize your disk. Try it while shining a flashlight on the disk, too! Ages 8+. (#9616) A ComputerGear exclusive. Item in stock unless noted above.