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Author Topic: Why does my folded thin card straighten when it it squeezed.  (Read 7127 times)

Offline Chemistry4me

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I was doing this with a bookmark the other day, folding it down the middle many times one way then the other, and I noticed that when the bookmark is bent at around 90 degrees or below and I squeezed the area under the fold the bookmark straightened.







I noticed that when done with a thinner piece of paper or a wider one it did not work as well, why is this?  :-\
Thank you for your attention.


 

Offline Karen W.

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Why does my folded thin card straighten when it it squeezed.
« Reply #1 on: 27/04/2009 08:03:18 »
Well that is interesting....It reminds me of a crease in metal...like say on a car thats been scrapped and slightly dented into a crease...? some times you can put a well placed two by four behind the crease or dent and smack it just right anbnd it will pop it right back out....but for some reason if the two by four is not just right on the crease then it misses and only partially straightens it out!
I just donT know..maybe its the counter pressure in the fold braces it or something!
 

Offline Chemistry4me

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Why does my folded thin card straighten when it it squeezed.
« Reply #2 on: 27/04/2009 09:15:16 »
What is a two by four? ???
 

Offline dentstudent

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Offline Chemistry4me

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Why does my folded thin card straighten when it it squeezed.
« Reply #4 on: 27/04/2009 11:31:20 »
What?
 

Offline JimBob

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Why does my folded thin card straighten when it it squeezed.
« Reply #5 on: 27/04/2009 16:05:37 »
2x4 a piece of lumber 2 inches by 4 inches. It is the standard size of framing material for buildings and homes.
 

Offline Karen W.

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Why does my folded thin card straighten when it it squeezed.
« Reply #6 on: 27/04/2009 16:28:34 »
Thanks Jimbob! LOL...I forget those over the pond  who are not well versed in our building supply lingo etc.... lol...
 

Offline Karsten

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Why does my folded thin card straighten when it it squeezed.
« Reply #7 on: 27/04/2009 17:14:53 »
Ironically it is not 2 by 4 inches once you get to use it. These are the dimensions BEFORE planing. Once in use a 2x4 is 1.5 inches by 3.5 inches.
 

Offline dentstudent

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Why does my folded thin card straighten when it it squeezed.
« Reply #8 on: 27/04/2009 17:15:52 »
Ironically it is not 2 by 4 inches once you get to use it. These are the dimensions BEFORE planing. Once in use a 2x4 is 1.5 inches by 3.5 inches.

Tell me about it :(
 

lyner

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Why does my folded thin card straighten when it it squeezed.
« Reply #9 on: 27/04/2009 19:28:25 »
What is a two by four? ???
God - the youth of today! The stuff they don't know. There will never be such a cuddly way of describing timber using SI units. Does NZ use SI?
 

Offline JP

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Why does my folded thin card straighten when it it squeezed.
« Reply #10 on: 27/04/2009 22:34:26 »
One possible explanation would be that the material the card is made out of likes to resist stretching or creasing.  When you bend it, the best shape to avoid doing either of those things is to straighten up and become basically part of a cylinder. 
 

Offline Chemistry4me

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Why does my folded thin card straighten when it it squeezed.
« Reply #11 on: 28/04/2009 06:01:47 »
Does NZ use SI?
Doesn't everybody? Yes.
 

Offline Chemistry4me

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Why does my folded thin card straighten when it it squeezed.
« Reply #12 on: 28/04/2009 06:06:01 »
One possible explanation would be that the material the card is made out of likes to resist stretching or creasing.  When you bend it, the best shape to avoid doing either of those things is to straighten up and become basically part of a cylinder. 
I've tried doing only one or two folds and it doesn't work. It only seems to work when I have really weakened it. Also if I squeeze it in the other direction, it bends in the other direction, i.e it folds together. Any ideas why? Now that I know what a 2 by four is. :)
 

lyner

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Why does my folded thin card straighten when it it squeezed.
« Reply #13 on: 28/04/2009 09:35:16 »
Does NZ use SI?

Doesn't everybody? Yes.

US seem to be  entrenched in ( our!) Imperial system, along with some parts of our language.
« Last Edit: 28/04/2009 09:37:35 by sophiecentaur »
 

Offline Karen W.

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Why does my folded thin card straighten when it it squeezed.
« Reply #14 on: 28/04/2009 10:31:29 »
LOL...LOL...zing!! lol....

 Hey C4M. +s that marker about cardstock thickness or thicker?

I want to try the folds to get a better hands on bendy folding "luff" as Neily might say!
 

Offline Chemistry4me

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Why does my folded thin card straighten when it it squeezed.
« Reply #15 on: 28/04/2009 10:47:20 »
It's about as thick as three sheets of printing paper.
 

Offline Karen W.

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Why does my folded thin card straighten when it it squeezed.
« Reply #16 on: 28/04/2009 11:04:50 »
Ok Thanks..I will try it....
 

Offline LeeE

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Why does my folded thin card straighten when it it squeezed.
« Reply #17 on: 28/04/2009 14:53:32 »
This is an interesting observation, that can also be applied to n-dimensional spaces.

The folded paper/card, which we can think of as a two-dimensional plane surface, can only be bent in the dimension that it has (in effect) zero thickness because it is inflexible in the dimensions that it has size; you can't stretch it's length or width.  However, the effect of the fold is to swap two of the dimensions, at a clear boundary, so that the direction of bending now lies within one of the dimensions occupied by the plane of the paper/card.

Because the paper/card is inflexible in that dimension, the paper/card has to re-align itself to accommodate the bend.

Although space-time is flexible, it's still interesting to wonder whether this sort of effect can be applicable to it.
« Last Edit: 28/04/2009 14:55:25 by LeeE »
 

Offline Chemistry4me

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Why does my folded thin card straighten when it it squeezed.
« Reply #18 on: 29/04/2009 05:50:14 »
Wow, thanks Mr LeeE. :) That sounds a bit more complicated than I first thought. But if I squeeze it the other way the card bends the other way, why's that?
 

Offline JimBob

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Why does my folded thin card straighten when it it squeezed.
« Reply #19 on: 29/04/2009 12:39:16 »
It is just the finger strength built up pulling and squeezing "other" things.
 

Offline LeeE

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Why does my folded thin card straighten when it it squeezed.
« Reply #20 on: 29/04/2009 13:15:47 »
... But if I squeeze it the other way the card bends the other way, why's that?

What exactly do you mean by squeezing/bending "the other way"?  Do you mean along the same axis but squeezing it 'in' instead of 'out', so that the 'flap' moves down instead of up?

When you squeeze the paper/card, the thing you tend to notice most of all is that the center bows one way or the other, but the more important factor is that the edges have to move forward or backwards relative to the center.  It is the direction that the edges move, relative to the center, which dictates whether the 'flap' moves up or down.
 

Offline Chemistry4me

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Why does my folded thin card straighten when it it squeezed.
« Reply #21 on: 30/04/2009 06:08:46 »
... But if I squeeze it the other way the card bends the other way, why's that?

What exactly do you mean by squeezing/bending "the other way"?  Do you mean along the same axis but squeezing it 'in' instead of 'out', so that the 'flap' moves down instead of up?
Yes. But now I see.
 

Offline 112inky

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Why does my folded thin card straighten when it it squeezed.
« Reply #22 on: 05/05/2009 16:51:38 »
i too tried it and have the same question 
 

Offline Chemistry4me

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Why does my folded thin card straighten when it it squeezed.
« Reply #23 on: 06/05/2009 06:51:02 »
Ah, so many questions yet so little answers. :)
 

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Why does my folded thin card straighten when it it squeezed.
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