A Bridge to Nowhere

2.5 based on 14 ratings

Updated on Nov 09, 2011


2nd – 4th grades

Difficulty of Project

Less than $5.00

Safety Issues
Material Availability
Readily available
Approximate Time Required to Complete the Project

One to two hours to experiment with the construction of the bridge; one day to prepare the science fair display

To create a bridge between two chairs using books

  • 2 matching chairs
  • 20 hardback books (approximately 8 ½ x 11-inches)
  • Measuring tape

All bridges have a center of gravity. The center of gravity helps the bridge to be balanced and stable. The center of gravity is easy to locate when an object is symmetrical.

In this investigation, the center of gravity is explored.


center of gravity: the average location of weight of an object

span: the distance between the two ends of a bridge

compression: a force that works to shorten or reduce in length

tension: a force that works to lengthen


The center of gravity aids in the stability of a bridge.

Research Questions
  • How can you build a bridge between two chairs with books?
  • How does the center of gravity help balance and support a bridge?
  • What other factors are important in building a bridge?

  1. Gather the necessary materials.
  2. Set the chairs facing each other about one foot apart.
  3. Place one book on each seat so that the spine hangs over about one inch. Continue placing books on top of each other staggering them each about one inch until the books meet in the center.
  4. Experiment with how far apart you can put the chairs and still create a bridge with the books. Record the results.
  5. Experiment with how few books you can use to make a bridge connect the chairs when they are one foot apart. Record the results.


“How Bridges Work” by Michael Morrissey at www.howstuffworks.com

“Geometry of Bridge Construction” at http://www.faculty.fairfield.edu/jmac/rs/bridges.htm

“Bridge Technology” at http://ww.fhwa.dot.gov/bridge


“Building Big Bridges” at PBS.org

Nancy Rogers Bosse has been involved in education for over forty years â first as a student, then as a teacher, and currently as a curriculum developer. For the last fifteen years she has combined a career in freelance curriculum development with parenthood â another important facet of education and probably the most challenging. Nancy lives in Henderson, Nevada with husband and their three teenagers.

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