What you need:
- Tablecloth (make sure that at least one edge doesn't have a
hem)
- Flat tabletop
- Unbreakable plates, cutlery and cups
How to:
Steve Spangler shows
you how:
- Find a tablecloth with no hem, or cut a piece of cloth to use.
The more slippery the tablecloth, the better the experiment will
work.
- Spread out the tablecloth with one edge hanging off the
table.
- Hold onto the edge of the tablecloth with both hands. Pull
straight down, towards your toes. Practice pulling the tablecloth
straight down, as fast as you can.
- Set the table. Practice with unbreakable cutlery and plates
first. Build up to using more items.
- Pull the tablecloth out from under the kitchen items. Remember
to pull straight down, as fast as you can.
What's happening?
Ever heard of Newton? His
theories help us to explain why this trick works.
The key is inertia. The principle of inertia
states that an object at rest (one that isn't moving, like the
plates) stays at rest unless another force acts on that object.
In this case, the plates stay at rest because the force of you
pulling down on the tablecloth isn't enough to move them.
The principle of inertia also says that if an object is moving,
it will keep moving unless another force acts on that object.
Imagine you're in a car - you and the car are both moving. If
the car slows down gradually, you slow down too. The friction of
your body against the seat and other forces combine to help you
slow down.
If the car stops suddenly, inertia will keep you moving forward.
This is why you need to wear a seatbelt. Your seatbelt prevents you
from moving forward too far when a car stops suddenly.