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 Jun 24th 2008, 08:33 PM #1 Senior Member   Join Date: Apr 2008 Location: HK Posts: 886 Knife Suppose there is a knife with infinitely small width and it is able to cut anything. I use this knife to cut an object into smaller and smaller pieces, to a certain extent, would the object not being able to cut into smaller pieces?
Jun 25th 2008, 04:22 AM   #2

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 Originally Posted by werehk Suppose there is a knife with infinitely small width and it is able to cut anything. I use this knife to cut an object into smaller and smaller pieces, to a certain extent, would the object not being able to cut into smaller pieces?
(shrugs) If the knife itself has an infinitesimal width then we are ignoring quantum effects, so you can cut the pieces as small as you like.

-Dan
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 Aug 7th 2008, 08:07 AM #3 Senior Member     Join Date: Apr 2008 Posts: 815 I think you would reach to cut the object in such a way that all its elementary particles are separated. If you are herculean you would be able to cut even its protons and neutrons into quarks, but don't ask me what happens if you try to cut a quark! EDIT : In fact, after having thought more about it, you wouldn't be able to cut anything because if it's infinitely tight, the knife wouldn't be anything. But you can assume it has a very small width (much smaller than any elementary particle which is impossible) and then you wouldn't be able to cut anything and your knife would simply pass between the particles without being able to separate them. __________________ Isaac If the problem is too hard just let the Universe solve it. Last edited by arbolis; Aug 7th 2008 at 02:07 PM.
Aug 7th 2008, 03:18 PM   #4

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 Originally Posted by arbolis ...but don't ask me what happens if you try to cut a quark!
No comment!

 Originally Posted by arbolis EDIT : In fact, after having thought more about it, you wouldn't be able to cut anything because if it's infinitely tight, the knife wouldn't be anything. But you can assume it has a very small width (much smaller than any elementary particle which is impossible) and then you wouldn't be able to cut anything and your knife would simply pass between the particles without being able to separate them.

-Dan
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