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Thread: Why does metal bend, but not wood?

  1. #1
    Administrator CatInASuit's avatar
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    Default Why does metal bend, but not wood?

    This is probably some atom based answer involving molecules and yes I am aware that if you treat wood carefully you can get it to bend.

    But in general if I pick up a spoon I can bend it, if I pick up a pencil, it gets snapped in half.

    Why is that?

    PS: Comments on my heroic feats of strength will result in
    In the land of the blind, the one-arm man is king.

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    The Queen Zuul's avatar
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    It's been far too long since I took any chemistry, but I'll give it a shot.

    With metals, you have a material that can shift its atoms relatively easily and remain connected. These atoms are sharing metallic bonding, which is one of the major reasons why metals have the properties they do. One important aspect of a metallic bond is that there is a very strong attractive force between the atoms. So the atoms are less likely to come apart, yet their positions can shift even as they stay together, which on a macro scale allows bends. In alloys, you start to lose some of this elasticity because of the addition of new materials to a previously pure element, but in exchange you also gain greater strength.

    With wood, you're not dealing with one material, but with living (or previously living) structures that are greatly varied in physical properties and chemical makeup. When the wood has become rigid enough to no longer bend easily, you get breaks. Moisture can give greater flexibility by softening up the wood and allowing it to stretch, but it's a fundamentally different kind of bend than in metal.
    So now they are just dirt-covered English people in fur pelts with credit cards.

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    The Apostabulous Inner Stickler's avatar
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    Are you familiar with the electron sea analogy in metal? In most metals the outermost electrons, or valence electrons, are relatively free from their atom's nucleus. This is known as delocalization. (This is also why most metals are so conductive, the electrons are very free and able to transfer the energy readily from one electron to the next.) But it also allows the metal to bend because the electrons buffer the metal atoms from experiencing repulsive forces from the other atoms as they slide past and causing the material to shatter.
    I don't think so, therefore I'm probably not.

  4. #4
    Stegodon
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    Wood does bend. Its flexibility and light weight were why it was used for so long in aircraft construction. See this for some interesting wood bending info.

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    Stegodon
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    Yes it does, although it's not exactly what the OP was asking.

    My parent's old house had a spiral staircase, and it was interesting to watch how the handrail was made: the carpenters took a 20-25 foot length of standard handrail, tied a rope to it, and tossed it into the river in the back yard. Every few days they'd take it out and bend it a bit on this metal frame for a day or two, then put it back in the water. What had been a perfectly straight piece of wood eventually became this beautiful curved handrail!

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    Administrator CatInASuit's avatar
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    Thanks for the answers.

    tunaman, do you have any pictures of that handrail?
    In the land of the blind, the one-arm man is king.

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