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Can't tear something into three pieces

  1. Mar 12, 2008 #1
    Does anyone know what physical principle theoretically prevents something from being torn into three pieces from two forces being applied? (E.g. pulling on both sides of a piece of paper will never tear it into three pieces.)
     
  2. jcsd
  3. Mar 12, 2008 #2

    Andy Resnick

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    Yes, but breaking a piece of spagahetti by bending it will usually result in three pieces (I think Feynman describes this), so your assumption is wrong.

    There's some work out there on crack formation and propogation, the main result is that the stress field is locally concentrated near the crack tip, and this localizes the crack by relaxing the stress away from the crack tip.
     
  4. Mar 12, 2008 #3

    tiny-tim

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    See http://www.exn.ca/Stories/1998/05/06/54.asp (Discovery Channel): :smile:
    This web-page also explains why you can't do it for plain paper:
     
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