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Why is water heavier than it looks?

  1. Aug 26, 2012 #1
    Why?
     
  2. jcsd
  3. Aug 26, 2012 #2

    haruspex

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    I think this question belongs in the psychology section.
     
  4. Aug 26, 2012 #3

    Bobbywhy

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    Better Best, Welcome to Physics Forums!

    How heavy, exactly, does water look?

    Cheers,
    Bobbywhy
     
  5. Aug 26, 2012 #4
    Well, idk. You're able to easily move it around and stuff but when you try to pick it up it takes effort.
     
  6. Aug 26, 2012 #5
    Always slipping through your fingers?
     
  7. Aug 26, 2012 #6
    Would that make it heavy?
     
  8. Aug 26, 2012 #7

    BruceW

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    no, it's not easy to move around. Its inertial mass and gravitational mass are the same.
     
  9. Aug 26, 2012 #8

    Drakkith

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    Water moves around things because it is a fluid. (It is also a liquid)
    To quote wiki:

    How HEAVY something may be is related directly to its mass.
     
  10. Aug 26, 2012 #9

    Bobbywhy

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  11. Aug 26, 2012 #10
    Oh, ok. Well then can you explain that to me? Because a balloon full of air and a balloon full of water the same size basically look similar, but the one with water is much heavier. How is that so if they're taking up the same amount of space? Stupid question, I know.
     
  12. Aug 26, 2012 #11
    This may come as a surprise to you but your eyes are not scales. They detect light, not mass.
     
    Last edited: Aug 26, 2012
  13. Aug 26, 2012 #12

    Drakkith

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    For a gas like helium in a balloon, there are FAR fewer atoms of helium that will fit in the balloon compared with water. This isn't because helium is "larger", it is because helium is a gas normally. The atoms are flying around very quickly and don't stick together at all like water does. Water molecules attract each other and are much heavier than helium atoms are, so they are much harder to turn into a gas. (Which is why water is a liquid all the way up to 100 Celsius while helium is a gas unless you cool it to around -270 Celsius)
    See the following links for more.

    http://en.wikipedia.org/wiki/Liquid
    http://en.wikipedia.org/wiki/Gas
     
  14. Aug 26, 2012 #13

    Borek

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    My troll detector goes "ping". This is a question children in preoperational stage may ask - that means, up to 7 y.o.
     
  15. Aug 26, 2012 #14

    BruceW

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    I'm going to assume no troll, and say the answer is density. You can imagine the water balloon has got more stuff inside, even though it has same volume as the air balloon. The ratio of 'stuff' to volume is density. (Or, more technically than 'stuff', I should say mass). In an equation:
    [tex]density = \frac{mass}{volume}[/tex]
    And the density of different materials is different.
     
  16. Aug 26, 2012 #15

    sophiecentaur

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    I did wonder about this question, at first,Borek. But -
    Is this question to do with the fact that, when you try to move 'through' water, you don't need to 'move it all', just to push some of it out of the way, yet, when you try to lift it (in a bucket) you need to move it all? This contrasts with a solid brick. When you lift or move a brick, you have to move all of it. Our senses are used to dealing with Newton's second law for solids and we are familiar with the extra vertical forces due to the weight of all solid objects, when lifting them. On the Moon, things are a bit different and probably a bit confusing for a while.
     
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