Materials Required:
l Empty food can, such as a soup can
l Can opener
l Scissors
l Cardboard
l Pail
l Water
l Drinking glass
The help of one of your parents
Procedure:
- Ask one of your parents to cut away the bottom of an empty food can with a can opener so that both ends are open.
- Cut a piece of cardboard that is a little bit larger than the bottom of the can.
- Fill a pail with water. Hold the cardboard beneath the bottom of the can and push the can straight into the water. When the outside water level comes near the top of the can, take away your hand from the cardboard. The inside of the can will remain dry as the cardboard clings to the can.
- Now pour water slowly from a drinking glass into the can. When the water level inside the can is the same as the water level outside, the cardboard will break away.
This Is What Happens:
The empty can and cardboard act as if they were one solid unit in the water—the force of the water presses upward on the cardboard, keeping it pressed to the bottom rim of the can. However, when you add water to the inside of the can, you are creating an opposite force—a downward force—which balances out the water pressure in the pail, and the cardboard drifts away.
