You can seemingly make water float in a cup using a simple trick involving atmospheric pressure. Here's how:
The "Floating Water" Trick
This experiment utilizes a cup, water, and a playing card to demonstrate the power of air pressure.
Materials Needed:
- A glass or plastic cup
- Water
- An old playing card (or a piece of firm, smooth cardboard)
- A bowl (to catch spills)
Step-by-Step Instructions:
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Fill the cup: Completely fill the cup with water.
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Cover the cup: Place the playing card firmly over the mouth of the cup, ensuring it completely covers the opening. According to the reference, you should "Cover the cup with an old playing card, making sure that the card completely covers the mouth of the container."
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Invert the cup: While holding the card firmly against the cup, carefully turn the cup upside down over a bowl (in case of spills).
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Release your hand: Slowly remove your hand from the card. The water should stay inside the cup, seemingly defying gravity!
Why Does This Work?
The water doesn't actually float, of course. What happens is that the upward pressure from the atmosphere pressing against the card is greater than the downward force of gravity acting on the water inside the cup. This pressure difference holds the card in place and keeps the water from spilling. Surface tension also plays a minor role in helping to seal the card against the rim of the cup.
