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Does this force really exist?

  1. Aug 2, 2006 #1
    I was just serching true the local library and I fount this qouit old book on physical expriments and meserments. Smewhere in inside the avtor talks about a strong attractive force that accourse when you put two bodys with very smooth surfices close together. I wonder if any of you ever heard of something like theat?
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  3. Aug 2, 2006 #2

    Andrew Mason

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    If the surfaces are smooth and flat enough and free from contamination (oxides, dirt etc.), you should be able to join to pieces of metal or glass together by putting the surfaces together. If no air is trapped, the molecules of the two surfaces start sharing electrons, and you end up with a sort of weld where the two surfaces disappear. I am not sure what the name is for this.

  4. Aug 2, 2006 #3
    Thats pretty damn cool. Are there any real life examples of this happening?
  5. Aug 2, 2006 #4
  6. Aug 2, 2006 #5


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    I hav seen this happen with Si Wafers.
  7. Aug 2, 2006 #6
    it sounds simelar to those buildings on top of that mountain. it must be easier there because of lower air pressure
  8. Aug 2, 2006 #7
    Are there any videos of this events aveilable online?
  9. Aug 2, 2006 #8
    Wow cool i never heard about aphenomena like that.
  10. Aug 2, 2006 #9


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    Lenin, what you're referring to is a demonstration of the Van der Waals force. I remember doing it in high-school with a couple of perfectly machined steel pieces called Johansen Blocks (sp?). When you slide them into contact, rather than just push them together, they become essentially one piece of metal. You can hold one, shake it around, whatever, and the other will remain stuck to it. The bonds are not as strong as regular molecular ones, though, so you can with some effort slide them apart again, or maybe even snap them in two. As Andrew explained, it's due to electron sharing.
    Last edited: Aug 2, 2006
  11. Aug 2, 2006 #10
    Gecko's use this force to stick to walls, in fact. They have a network of extremely small hairs and pads which can stick to nearly any surface.
  12. Aug 3, 2006 #11
    Reminds me of the Anime Rurouni Kenshin, where he gets a kitchen knife made by an extremely skilled sword maker and cuts some vegetable in half so precisely that he just puts it back together and it's whole again! xD
  13. Aug 3, 2006 #12
    can u give me the experiment details? sound intresting, and if u did that at highschool, im sure that i could make the experiment at home...
  14. Aug 3, 2006 #13


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    This sounds like a parlor trick. Anything with moisture like food will naturally stick together. I'll bet it wouldn't stand up to the shear force from a stiff feather.
  15. Aug 3, 2006 #14
    Except it's a cartoon :-/
  16. Aug 5, 2006 #15


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    Not sure here; did the OP read about Van Der Waals Effect, or Casimir Effect? Could have been either one.

    Lenin, Casimir Effect is described here:


    Does this look like what you read about?
  17. Aug 8, 2006 #16


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    It wasn't an experiment, just a demonstration. The experimental part would be in seeing if you could machine the parts accurately enough. There can't be a variance greater than something like .0001 " over the entire contact surface of each block. At that time (35 years ago), it was quite expensive to have them made.
  18. Aug 8, 2006 #17
    I think this is how they did that super glue commercial where the guy is hanging from an I beam. His hard hat had a milled pice of metal joined to another that was attached to the beam.
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