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Super Bridge

Classroom Activity

Objective
To recreate some of the challenges bridge builders face.

• copy of "Bridge Building" student handout (PDF or HTML)
• coffee can
• 75 uncooked spaghetti noodles
• 2m (6.5ft) masking tape
• standard set of weights (fishing sinkers work well)
• 6 strips of corrugated cardboard:
  8 cm x 30 cm (3 in. x 12 in.)
  8 cm x 50 cm (3 in. x 20 in.)
  8 cm x 80 cm (3 in. x 31 in.)
  8 cm x 100 cm (3 in. x 39 in.)
  8 cm x 120 cm (3 in. x 47 in.)
  8 cm x 150 cm (3 in. x 59 in.)

1. One of the major challenges bridge designers face is constructing towers to support the bridge. In this activity, students build structures that recreate problems bridge builders face.

2. Organize students into small teams and distribute the "Bridge Building" student handouts and materials.

3. Have students design and build a tower structure using uncooked spaghetti that will support a coffee can. Have them find the maximum length of cardboard road the structure supports, add weights to their structures, and find the maximum road lengths again.

4. After each team has completed their structure, have the class compare and analyze each team design. Which design holds the most weight? How could the design that holds the least weight be improved? Which design balances the longest road? Which designs appears to twist and turn under weight? Which designs prevent twisting?

5. After analyzing each design, have students suggest two ways they would improve their designs.

Students may begin by placing individual pasta strands around the base of the can or by building a cube-like structure as shown below.

Students will discover that the best way to enhance the strength of pasta and prevent torsion is to make bundles of noodles and to use triangulation. The triangle shape, in combination with the bundles of noodles, greatly improves the tensile and compressive strengths of pasta. By adding weight to the can, students will find that the length of road the structure can support increases. The weight increases stability by compressing each leg of the triangle on its adjoining legs and preventing the materials from twisting.

Adding weight to the coffee can stabilizes the base of the bridge tower, which in turn stabilizes the cable structure that holds up the road. The weight prevents torsion of the tower and also acts as a huge compressive force so that the entire tower stays in place.