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Bizarre water compression in glass.?

If you half fill a straight glass, then put a beer mat or coaster on the top of the glass then turn it upside down, holding the mat/coaster on, the water compresses by approx 25%, if you don't believe me then try it.

My question is:

Why and how does this happen? i was always led to believe water can only compress by a very small fraction. It really is bizarre!!

3 Answers

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  • 1 decade ago
    Favorite Answer

    You are not compressing water, you are compressing air. Air on top of the water coulumn gets compressed when push the mat upwards.

  • 1 decade ago

    Erm.... Is the glass wider at the top than at the bottom?

    Basically no compression just fitting the same volume of water into a wider area.

    Simples!

  • 1 decade ago

    No, not possible. Water is not compressible.

    I don't know what optical illusion is deluding you, but something is.

    .

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