Gravity-Defying Water
Use a simple piece of card to manipulate gravity.
This activity may be Messy
Use a simple piece of card to manipulate gravity.
This activity may be Messy
What you'll need
Gather your supplies from the list above.
1.
Fill the glass with water.
2.
Place the card on top.
3.
Turn the glass over, while holding onto the card and making sure the card always stays flat. Do this over the plastic tray.
4.
When the glass is upside down let go of the card… and it should stay where it is!
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What happens if you tip the glass? Does the seal still hold?
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Does it work better with more or less water?
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What happens if you use a plastic cup with a hole in the bottom? (Cover the hole with a finger while you fill the cup.)
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What is stopping the water from coming out?
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Will the seal hold for ever?
The weight of the water inside the glass presses down on the card, but there is another force pressing upwards on the card from outside: atmospheric pressure. The atmosphere is more than 100 kilometres thick, and the weight of all that air above means that, at ground level, the air pushes on everything, in all directions.
The atmospheric pressure on the underside of the card is strong enough to counteract the pressure of the water pushing downwards – until the card becomes sodden and soft, and the water begins to leak out around the rim of the glass.
Atmospheric pressure varies, and that variation affects the weather. High pressure normally brings settled weather, but things become unsettled and stormy when the pressure drops. A barometer is a device that measures atmospheric pressure and can therefore help in predicting how the weather will change.
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