The Inert Coins
You will need: Three coins, water glass, paper, and ruler.
Have you ever seen a magician snatch a cloth from a table, leaving all the crockery and cutlery still in position? This feat is made possible by the condition known to scientists as 'inertia.' The cloth was whipped away so quickly that the articles on top of it were left comparatively undisturbed.
You can perform the same trick on a smaller level.
First, cut a long slip of drawing paper, place one end on the edge of a glass and balance three coins on top of it, as shown in the photo.
You can now remove the paper without touching the coins and still leave the latter balanced on the edge of the glass. If you pull the paper slowly, the force you use will not be enough to overcome the inertia of the coins.
So grip the free end of the paper and raise it until the paper is horizontal. Then take a ruler and strike sharply downward at the paper, about 1.5- inches away from the coins. So quickly is the paper whipped from under the coins that their inertia is undisturbed and they remain balanced on the edge of the glass.