Science Projects And Inventions

YOU NEED:

• A large nail
• A plastic bottle
• A balloon
• An unsharpened pencil

Pierce a hole near the bottom of an empty hard plastic bottle with the nail. Spread a balloon over the mouth of the bottle, as in the illustration. Now inflate the balloon and put your thumb over the hole in the bottle. Unaware of the hole, your friends are puzzled because the balloon remains bloated. Hold the bottle at arm's length with the top of the bottle pointing to the roof. Insert an unsharpened pencil into the balloon and count till three. At three remove your thumb deftly from the hole. The balloon will deflate sending the pencil soaring into the air.

 HOW DOES IT WORK?

When the balloon is inflated inside the bottle and your finger covers the hole, at the bottom of the bottle, it a partial vacuum is created preventing outside air from rushing in. Once you remove the finger, the vacuum is removed and the balloon deflates so rapidly that it throws out the pencil.