F I pinch hold a book, with 6N on either side

1. May 13, 2013

dgamma3

If I pinch hold a book, with 6N on either side why is there only one force, of 6 newton on the free body diagram?

for example, the book has this free body diagram. http://i.imgur.com/pwtFZB6.png

there are two forces applied to each side of the book. so why is it, than in the free body diagram, there is only 1 force (of 6N). shouldn't you have two forces pointing away from one another, one with 6N (pointing right) and the other with -6N (pointing left), which would cancel out?

Edit: this is the explanation in the book.
Consider the free-body diagram below. The force of the fingers on the book is the reaction
force to the normal force of the book on the fingers, so is exactly equal and opposite the normal force on the fingers.

thanks
daniel

2. May 14, 2013

haruspex

I would guess that the F in the right hand picture should be an n.

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted