Activities Index | Handout | Educator Ideas
(per group of two)
plain paper (such as photocopier paper)
5 paper clips
2 books or blocks
at least 100 pennies, metal washers, or other small weights
After the activity, show "Environmental Loads" from Bridges to spark kids' ideas for modifying their bridges. (Check the Program Description to locate the show segment.)
Try the Shapes Lab.
For more information, see Additional Resources.
Introduce the Activity
Hold up a single piece of paper. Ask: How many pennies do you think a bridge made out of this paper can hold? After kids make some guesses, lay the sheet of paper flat across two books placed 20 cm (about 8 in.) apart. With the kids keeping count, place pennies on the bridge, near the middle, until the bridge fails. (It will hold only a few.) Now introduce the activity challenge.
Lead the Activity
Ask kids questions about their designs. What can they do to the paper to make it stronger? Should they cut the paper? How can they use the paper clips? (Kids may accordion-pleat the paper, roll it, or cut it into strips and weave them together. The paper clips could be used to stiffen folded paper.)
Have a discussion about different types of bridges kids have seen. How long were they? How tall? What were the bridges designed to transport (e.g., trains, cars, people)? What other considerations went into designing the bridges (e.g., earthquakes, boat traffic)?
As kids test their bridges, suggest that they observe the bridges closely to determine where they fail.
The Big Idea
Changing the shape of a material can change the way it resists forces. Although a piece of paper seems flexible and weak, it can be folded, rolled, twisted, or otherwise altered to support quite a bit of weight. Folding the paper helps it to resist bending forces created by the live load of the pennies on top of the bridge. The paper can be folded into the shape of an I-beam or accordian-pleated, as shown below. Rolling the paper around the pennies and fastening the ends with paper clips is another possible solution.
Build on It
Use this opportunity to discuss that while engineers cannot build multiple full-size bridges to test their ideas, they use models and computer simulations to test and redesign structures.
Possible outcome: Kids will probably find that the bridge can support more weight distributed along the bridge than at a single point.
Social Studies Have small groups of kids each choose a bridge featured in the video or another large bridge. Each group should create an advertisement for their bridge that highlights what they think is most important to the people in the bridge's community. Encourage kids to use both text and images to convey their message.