Bridges

Opening Discussion

Set the context by asking kids about bridges they’ve seen before. What are bridges used for? What kinds of things do they help us get across? What kinds of things cross bridges (cars, bicycles, people, etc.)? What do they think makes bridges strong? If possible, show them some pictures of bridges, or even better, take them on a walk to a bridge that is nearby. You could also ask a couple of volunteers to draw on chart paper a bridge they’ve seen before.

The Challenge

Tell your students that you’d like them to be bridge engineers and create a bridge using just 5 sheets of recycled paper and a small amount of masking tape. Their bridge will need to cross over 8.5 inches of “water” (a gap of 8.5 inches between 2 books or boxes), it cannot touch the “water”, and it cannot be attached to the “river banks” (the books or boxes). The 8.5 inches will be easiest to measure if you place a standard-sized piece of paper in between the 2 books or boxes, as these pieces of paper measure 8.5 inches wide. The students can color this paper to look more like water. Testing the strength of the bridge will be done by placing the coffee can or take-out container on the bridge and adding weight until the bridge collapses.

Doing the Activity

1. Divide your children into teams of 2-3. Describe the challenge and the rules of this activity.
2. Have each team select a “buyer”, who is the person in charge of picking up the materials and bringing them back to the team, and have the buyers collect the paper, coffee can, washers or pennies, tape and books or boxes.
3. Have them start building! Pay attention to the shapes that the teams are using to construct their bridges. Do you notice any teams using triangles (accordion folds)? Or circles (tubes or cylinders)? Make sure to allow children to build with minimal suggestion from you—your role is to ask questions, not give answers!

Let’s Talk About It

Once each team has created and tested at least one bridge, bring them together to discuss their findings. Have each team share what they’ve tried so far and what their results have been. This discussion should last no more than 10 minutes.

Build On What They Talked About

Send your students back to their bridges and have them create a new design or refine their old one based on what they learned from the discussion with the other teams.

SESSION 2

A few days after trying the bridges activity, introduce a new challenge:

1. Review what your students did last time, focusing especially on the shapes they used to build strong bridges. Challenge them to try again to build an even stronger bridge.
2. If some teams build their bridges using triangles (the accordion shape) and some with circles (tubes), you might try having the whole group work just with one of those shapes and see how they can build the strongest bridge possible. Then try the other shape. With both kinds of bridge you will find that the smaller the circles (tighter tubes) or the smaller the triangles (as many accordion folds as possible), the stronger the bridge will be. After experimenting with these shapes have each team make a final bridge, with the goal of making it as strong as possible. As a culminating activity, you can have each team bring their bridge to the front of the room and test how much weight it will hold. Record the results and compare the strongest bridges to the others—did the strongest bridges have anything in common?