Designing Your Own Paper Bridge Lessons

In designing your paper bridge lesson plan, your probably won't get very far without doing the activity yourself. Just as students need to become familiar with the materials they are designing with or the product they are redesigning, you'll need hands-on experience with the paper bridge task. The Challenges In Physical Science textbook provides a pre- and post-test for students. These paper-and-pencil tests can help you in assessment, and can help students by getting them to recall similar structures like fences and full-scale bridge. A Formative Assessment task you might ask your students to do mid-unit is to predict which of the model bridges (see below) will fail first, and then explain why. Watch MOVIE 1 to hear about materials and teaching tips you will need to do this activity.

Most successful bridge designers focus on changing two variables — the height of the paper bridge, and the location of the hanging bottle(s). These choices determine the angle or slope of the bridge, which affects how much tension the bridge's diagonal arms must support. More tensile forces means the bridge will need more material to avoid failing. Students may prefer bridges with short arms, but they must be made so thick that the overall bridge is much heavier than a longer, much more slender-armed bridge. In sum, successful model bridge designs have diagonals that are as nearly vertical as possible. Deep V-shaped bridges can be made with the thinnest arms. With this in mind, students need then to focus on where the paper should be reinforced. Have them look for places where the paper has more stress lines or where it is about to or did fail. Such areas should be reinforced by making them thicker and/or wider.