Monday, December 29, 2014

Pulling Apart Two Magazines - Paper Friction

How much friction is there people two pieces of paper?  Answer:  Not much.  You can easily test this by placing one piece of paper on top of another and then pull the two pieces apart horizontally against each other.  The two pieces easily slide apart.  But what if you add more pieces of paper?  A really cool experiment to test this can be done using two phone books or two magazines.  My daughters and I grabbed two magazines and started interweaving the pages together.  One page from one magazine on top of the other page, and continue until the two magazines are interwoven page by page.

Now have on person grab one magazine binder on one side and a second person grab the other binder on the other side.  Now pull horizontally.  Do the magazines come apart?  If you pull hard enough, yes, but you have to pull very hard.  The greater the number of pages, the harder it is to pull apart.  My daughters gave it a try and were unsuccessful as you can see in the video below.

We then picked up one magazine and held the bundle vertically to see if gravity could do the trick.  No luck.

The friction force between any two pages is small, but add it up over all of the pages and the force is very large.  Mythbusters did this once with two phone books and ropes and chains were breaking while the books stayed stuck together, simply from the friction force of paper on paper.  

Give it a try, your kids will find it very cool!

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