Book Balance
How Can You Make a Stack of Books Lean Without Falling Over?
Materials
- 6 to 8 books
Try This
- Place one book about 1 foot (30 cm) from the edge of a table.
- Place a second book on this book but position it to extend over the first book just enough to balance.
- Place a third book on the second book in the same way.
- Continue stacking the books in this way until you have used all the books. Be sure to balance the books so they do not fall over. What happens as you add books?
What's Going On?
When you stacked the books in this manner, the books acted as though they were one object and stayed as a stack until the center of gravity was no longer supported by the bottom book. As you added each book, the center of gravity changed. But as long as the center of gravity was supported, the books did not fall over. A structure anchored at one end this way is called a cantilever. Tree branches and apartment balconies are cantilevers. When the center of gravity was no longer supported, the books tumbled over. Structural engineers use this knowledge when they design things like bridges.
