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If you look at the top of the water in this tumble, you'll see that the edges ever so slightly curve upwards. |
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The water has a kind of skin on it, caused by surface tension. |
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It's called the meniscus, and you can use it to play a game with your friends. The aim of the game is to place objects into the tumbler, with the first person to make the water spill over the top edge being the loser. |
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You need a glass tumbler with a round and even lip to it. It mustn't have any chips in it, and it needs to be clean - no traces of washing up liquid, for example. |
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Find a nice, flat surface, and fill the tumbler right up to the top. |
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Take alternate turns to drop 2p coins into the water. You'll see that instead of spilling down, it starts to go up and bulge above the rim of the glass! |
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Eventually, it will spill, however! |
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