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Science Project: Cantilever Bridge Viewed: 5021
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Cantilever Bridge

Cantilever bridges are built with two beams that project toward each other to join and form a span. How do they stay up?

You need:

  • 5 or 6 notebooks or thin books
  • table

What to do:

Stack the notebooks on the edge of a table. Slide the top one halfway out from the stack and over the table's edge. When it balances, slide it back a little. Move out the next notebook along with the top one until they balance, and then slide them back a little. Add another notebook and move the top 3 out and slide them back a little after they balance. Continue in the same way until all the 5 or 6 notebooks are staggered.

What happens:

The top notebook seems to be suspended in air, but the notebooks do not fall.

Why:

You have found the center of gravity, the point at which all the weight of an object seems to be con­centrated. Though the top book appears to be sus­pended in air, more than half the weight of the stack of notebooks is resting on the table.