At home for 5-11 11-14
- Level Elementary
What you need
- A balloon
- A little water
- Two plastic cups
- A friend
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.
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.
These experiments have not been specifically safety tested for home use but we believe them to be safe if the instructions are followed. Adult supervision or direction is recommended as appropriate. All experiments are carried out at your own risk.