This article was taken from the June 2014 issue of Wired magazine. Be the first to read Wired's articles in print before they're posted online, and get your hands on loads of additional content by <span class="s1">subscribing online.
It's the party trick we all want to be able to do -- and might have attempted after too many glasses of wine. Whipping a tablecloth from a beautifully laid table so quickly that not one tumbler tumbles. It's not magic -- it's physics. "Part of what makes this stunt so satisfying is that the potential for epic disaster is very real," says Fritz Grobe from viral-video studio EepyBird, which showcases DIY science experiments.
Lay the table
Select your tablecloth (as slippery as possible and without a hem) and glasses/dishes/cutlery (the heavier, the better). "Both these tips will help inertia win over friction and make the stunt go smoothly," says Grobe.
Hold your tablecloth
Grip the cloth firmly with both hands. The stunt will be easier if you make sure relatively little cloth is hanging down on the side furthest away from you, because you will have less to pull out from under your table setting.
Tug with confidence
Yank the cloth quickly in a downwards motion (pull upwards and everything will go flying). "The edge of the table will redirect the force straight along the surface, ensuring that the cloth slides straight out," says Grobe.
How does it work?
This works because of inertia -- the principle that an object at rest remains at rest unless a force acts upon it -- versus friction. The greater an object's mass, the greater its inertia, and the more force required to overcome it. The sharp tug generates enough force to overcome the friction between the cloth and the setting. A similar trick involves an egg balanced on a paper tube on a sheet of cardboard, resting on a glass of water. Smack the card away and the egg will fall into the glass. Smooth.
This article was originally published by WIRED UK
