Balancing the Books
Printer-friendly versionLast Tuesday, we came up with the idea of guessing how many books can be placed at the edge 1/10 of the table before they topple down. We realize it takes a little bit more than half the books to be on the table before the pile goes down.
First we estimate that it takes 6 books before toppling down.We carry out an experiment. It actually took 5 books, just as the hint suggested. So it can't be above 5 books to be placed on the edge 1/10 of the table.
My friend and I found this an interesting puzzle 
We used exercise books. Maybe you can try using a thicker book to see whether it works or not. Have fun !
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Puzzle Name:
Balancing the Books
Description of Puzzle Solution:
The center of mass of the pile of books should not go over the edge. Once the center of mass is over the edge, then the whole stack of books falls. => Stack can`t made so that the upper edge of the book is a table. The top book can not be located beyond the edge of the table for more than half its length.
Distance (from its length) to which the book should act can be calculated by the formula 1/2N, where:
N-number of books in the stack. For example, if we have 5 books it should appear on 1/10 of its length and this stack will not fall.
How the solution was found:
The solution was found by determining the center of mass. Considered this problem from the standpoint of physics.
How interesting and challenging the puzzle was:
Yes. The task was easy.
Advice for someone else working on the same puzzle:
See the definition of center of mass.