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Science Project: Why No Flood? Viewed: 3383
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Why No Flood?

Until you learn how to work this experiment per­fectly (and maybe even then), it's best to work it over a sink or basin.

What you need:

a piece of cardboard or a large index card

What to do:

Place the cardboard over a drinking glass filled to the brim with water. Make sure no air bubbles enter the glass as you hold the cardboard against it. Then turn the glass upside down over a sink or basin. Take away the hand holding the cardboard.

What happens:

The cardboard stays in place and the water stays in the glass.

Why:

The pressure of the air outside the glass is greater than the pressure of the water inside. It is the air pressure that keeps the water in the glass.