Bridges illustrate the effect of weight or another force at a distance from a pivot or support point (torque), and they also provide experience with beams.

ASK

**How might we use a weak material like PAPER in order to MAKE A BRIDGE strong enough to span an 8 inch gap and support a weight?**

- 8 1/2 x 11 scrap paper
- small weights
- ruler
- books in even height piles, 8 inches apart

IMAGINE

Think about different shapes, structures and forms – folds, tubes, beams. It must be long enough to cross the gap made with a single piece of paper.

PLAN, CREATE

- Take a sheet of paper and construct a bridge which will span an 8-inch gap (piles of books). Do not use any materials to anchor the bridge to the desks
- Experiment by adding small weights, one at a time, to the center of the bridge.
- When the bridge collapses, try to construct an even stronger bridge, using another sheet of paper.
- Keep a record of the trials. Draw the shape of their bridge and mark down how much weight each bridge held before collapsing.
- Draw a cross-section of the bridges, as well as a silhouette. Look closely at which constructions were successful and which were not.

IMPROVE

Which were discovered to be successful? What were the improvements?

- 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?