What Makes a Stone Skip When Tossed Across a Pond?

Discussion in 'Hydrodynamics and Aerodynamics' started by Submarine Tom, Mar 29, 2012.

  1. MikeJohns
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    MikeJohns Senior Member

    You mean light transmission? Similar to Apollo 13 reentry angle.

    I's just a matter of lift as others posted.

    Also for interests sake glass is not technically a liquid, it's real definition is a non crystaline amorphous solid. The idea that it can be considered a supercooled liquid vaporized decades ago along with the theory that it flows over time.
     
  2. rxcomposite
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    rxcomposite Senior Member

    I said to give it as MUCH BOUNCE AS POSSIBLE. If you want to give your kid a cannon, that is fine with me.:p
     
  3. hoytedow
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    hoytedow Wood Butcher

    It is a highly viscous fluid. Old window glass shows the flow from the effects of gravity with the effect that the glass "pools" at the bottom and thins at the top. Your amorphous solid statement reflects the wiki article which I referenced in my earlier post.
     
  4. Leo Lazauskas
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    Leo Lazauskas Senior Member

    It's another one of those myths that just won't go away...

    The thickening at the bottom of those windowpanes would take at least
    10^19 years. I guess that's longer than the 6000 years the world has
    existed according to some befuddled types, so they reject it.

    See, among other scientific papers:
    Y.M. Stokes, "Flowing windowpanes: fact or fiction?"
    Royal Society Proc. A: Mathematical, Physical and Engineering Sciences,
    455, 1999, pp. 2753-2758.
     
  5. Ad Hoc
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    Ad Hoc Naval Architect

    Just a few then!

    The 'flow' is technically called "devitrification".
     
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  6. Leo Lazauskas
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    Leo Lazauskas Senior Member

    Earlier estimates put it at 10^32 years.
    There are many other references, but I only included the one which thanks
    me for pointing out the myth :)

    My erstwhile colleague E.O. Tuck made the same mistake and was shocked
    to learn he was spreading unmitigated bulldust. It led Stokes to write that
    paper and eventually earn a PhD under his supervision.

    I have absolutely no faith that it will stop the myth from being propagated -
    "it must be true because my science teacher/priest/stockbroker said so AND
    I read it on the internet."
     
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  7. MikeJohns
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    MikeJohns Senior Member

    You have bought into an Urban Myth I'm afraid. Glass doesn't flow it doesn't even 'Creep' under load. The ancient Egyptian glass bottles are still as they were made all those thousand of years ago ! Otherwise they would be puddles.
    Window glass is a good example, the fact that some is thicker on the top and some on the side and most on the bottom proves that the glaziers tended to install the thickest part on the pane the lowest. That's all.

    But as Leo posted it's now well proven that it's baloney and the urban myth needs killing. So kill it whenever you see it.
     
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  8. rxcomposite
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    rxcomposite Senior Member

    Without deviating from the topic, can anybody explain why when adding cornstarch, (a non Newtonian. or anti Newtonian material) to the water makes it resist impact but remain a fluid?

    There were two explanations.

    1. It holds the molecules of water making it "unstretchable".
    2. The molecules tend to close together when impacted, increasing its density.

    I have seen the demonstration but it is the explanation that does not sit well with me.

    Which one is the correct one?
     
  9. Ad Hoc
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    Ad Hoc Naval Architect

  10. yipster
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    yipster designer

    Open that urban mith pdf later reading this on my mobile
    thixotroop, is that also the reason you can cut glas under water
    witbh a scissor? (even at the bottom of a bucket water)
    chew and swallow it and more? will check I-net and be back
    dont start on extra toughed glas as thats much harder to scissor
     
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  11. MikeJohns
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    MikeJohns Senior Member

    While we are at it and considering that the stone skip has been well answered:

    There is some supposed saints blood that gets shaken into a liquid each year, also a thixotropic change. Good for business some of these awe inspiring tricks.

    That is an iron gel from memory. It solidifies but liquifies when shaken.

    Yipster
    I didn't know that, I found this explanation but I'm not saying it is correct:

    "water causes glass to crack more easily because when a water molecule enters the crack, a reaction occurs in which a silicon-oxygen bond at the crack and an oxygen-hydrogen bond in the water are cleaved, creating two hydroxyl groups attached to silicon. As a result, the length of the crack grows by the size of one bond rupture. The water reaction reduces the energy necessary to break the silicon-oxygen bonds, thus the crack grows faster."
     
  12. yipster
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    yipster designer

  13. hoytedow
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    hoytedow Wood Butcher

    You got me.
     
  14. MikeJohns
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    MikeJohns Senior Member

    If you'd listened to what your mother had told you, you wouldn't get into these messes :)
     

  15. hoytedow
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    hoytedow Wood Butcher

    I blame my high school chemistry teacher, God rest his soul. :)
     
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