Sliding tablecloth out from under posh dinner setting.
What it shows:
A body will remain at rest unless a force acts upon it. So too will your best china remain in place as the table cloth is whipped from under it providing the friction between the cloth and table setting is low, and the speed of removal high.
How it works:
The necessary requirements for a successful removal of the cloth are speed and low friction. The cloth is a smooth cotton (no hems!) 120 × 50 cm , the dinner setting real bone china, glass and metal which are nice and heavy so you get the inertia i.e. resistance to motion. With the long cloth you can make a neat 50 × 50 cm table cloth and have over half a meter spare to get a good grip of the end. Stand at arm's length to the bench and take up the spare cloth in folds with both hands so that the cloth beneath the setting is taut. With one swift, continuous move, bring your hands horizontally into your body; the cloth comes with them and the setting stays.
Setting it up:
On the end of the lecture bench, lay out the dinner plate, knife, fork and tumbler (a wineglass is pushing your luck). Let the extra material drape down the side of the bench ready to be taken up by the lecturer. A correct setting is important (especially at Harvard) and we recommend studying the reference before the demonstration is attempted.
figure 1. Proper table setting
Practice first! The snap removal of the cloth cannot be done timidly.
Elizabeth L. Post, Emily Post's Etiquette, (Harper Collins 1992) 15th ed., p 426