Atmospheric Pressure
Properties of Matter

Facing Pressure

Enrichment Activity for 5-11 11-14


What you need

  • A balloon
  • A little water
  • Two plastic cups
  • A friend

Instructions

  1. Blow up the balloon to grapefruit size. Get your friend to wet the rims of the cups and hold them firmly against the balloon, one on each side.

  2. Inflate the balloon to normal size then ask your friend to let go of the cups.

Results and Explanation

The cups will stick tightly to the balloon without help, and if you draw a face on the balloon the cups it will look like ears.

At first the balloon dips deep into each cup, but it flattens out as you inflate it, taking up less space in the cups, so the air pressure inside them drops. The air pressure outside them is unchanged, so it presses them firmly against the balloon.

Atmospheric Pressure
is a special case of Pressure
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