Technology

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Materials

• 100 popsicle sticks
• 100 toothpicks
• 1 small bottle of wood glue
• 1 pack of dental floss

Procedure

From the material you have been assigned, build a bridge as strong as possible. Use wood glue to glue popsicle sticks together. Test your bridge by placing it between two tables and placing books on it. You can turn this into a competition, where the team who builds the strongest bridge wins.

Here are examples of bridges from around the world:

Short explanation

A bridge is a passage over water or another obstacle. The design of the bridge is crucial for its strength.

Long explanation

There are many different types of bridges, such as suspension bridges and arch bridges. To learn more about each type, I recommend the Wikipedia article on bridges. Which bridge that engineers choose to build depends, among other things, on the budget, the terrain where you are going to build, what the bridge will be used for and what material you are using.

Regardless of the type of bridge, a truss is a solid and economical construction method. A truss consists of straight bars that are assembled into triangles. When three bars are assembled as a triangle, the shape of the triangle cannot be changed, which makes trusses very stable. This can be compared to four bars assembled as a square - which can be pressed together even if the bars are still connected. In a truss, the nodes, i.e. where the bars are connected, are considered to be movable like hinges. This means that each bar is only exposed to pressure or tension, i.e. forces that either try to shorten them or stretch them longitudinally. There are no forces trying to bend the bars.

Deformation is, in technology and engineering, a change in the size or shape of a body when it's subjected to a force or a change in temperature. In this build, the bridge is deformed when subjected to a pushing force, more specifically something heavy on the bridge. The deformation of the bridge consists in the wood (mainly lignin and cellulose) changing its shape or breaking apart. The bridge can withstand a certain amount of deformation without breaking, but if the load is too great, a popsicle stick or node breaks.

Test and improve

You have now built your first prototype. There are probably improvements to be made. In order to keep working on your design, try answering any of the following questions.

• Where does your bridge break when it's overloaded??
• How can you build a bridge that you can stand on?
• How can you build the longest bridge from the material you have been assigned?

Variation

If you really want to challenge yourself, you can use uncooked spaghetti instead of popsicle sticks.

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