With some practice, you too can do this stunt. Choose a slick, unhemmed tablecloth,
one with no flaws that might catch on the dishes. A supple fabric such as silk helps because
you can then pull the cloth slightly downward at the edge of the table. When you get up the
nerve to try—with unbreakable dishes, of course—make sure that you pull suddenly and
swiftly, so as to minimize the time it takes for the cloth to slide out from under the dishes.
Leaving a little slack in the cloth at first helps you get your hands up to speed before the
cloth snaps taut and begins to slide off the table. Don’t make the mistake of starting slowly
or you’ll decorate the floor.
Give the tablecloth a yank and watch what happens. With luck, the table will remain
set. If it doesn’t, try again, but this time go faster or change the types of dishes or the way
you pull the cloth.
If you don’t have a suitable tablecloth, or any dishes you care to risk, there are many
similar experiments you can try. Put several coins on a sheet of paper and whisk that sheet
out from under them. Or stack several books on a table and use a stiff ruler to knock out the
bottom one. Especially impressive is balancing a short eraserless pencil on top of a wooden
embroidery hoop that is itself balanced on the open mouth of a glass bottle. If you yank the
ring away quickly enough, the pencil will be left behind and will drop right into the bottle.
The purpose of this experiment is addressed in a simple question: Why do the dishes
stay put as you remove the tablecloth? We’ll return to that question at the end of this chapter.
In the meantime, we’ll explore some of the physics concepts that allow us to answer it.