Paper Bridges

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Ask the students to take a sheet of paper and construct a bridge which will span an 8-inch gap between desks. They should not use any materials to anchor the bridge to the desks.

When the students have achieved this first step, ask them to experiment by adding small weights, one at a time, to the center of the bridge. When their bridge collapses, have the students try to construct an even stronger bridge, using another sheet of paper.

Keep a record of the trials. Ask the students to draw the shape of their bridge and mark down how much weight each bridge held before collapsing. In addition to having them write down "five pennies" or "three paper clips," have the students measure the weights of the pennies, paper clips, or whatevers, on a scale, and record the loads on the bridges. Have the students draw a cross-section of their bridges, as well as a silhouette, so that they will be able to look closely at which constructions were successful and which were not.

Have the students share their particularly strong or weak bridges with the rest of the class. Discuss and chart the shapes which were discovered to be successful. Ask the following questions:

• What shape seemed to be the weakest/strongest?

• What part of the bridge seemed to collapse first?

• Where was the bridge weakest?

• What would you use to make the paper bridge even stronger?

• What do you think would happen if the desks were farther apart? Closer together? Why?

• What do you think would happen if you could anchor the bridges to the desks? Why?