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Background
When you think of bridges, you probably don't think of a dinosaur. Did you know that the structure of a dinosaur can be compared to a bridge? When you built your "bridge" out of fettucini, you learned about how bridges can support weight. Now, we are going to see how this knowledge of physics can be used to discover the answers to other questions.
How do they know that dinosaurs held their tails erect? What's the physics?
When museums first began displaying dinosaur skeletons, they were assembled with their tails laying flat on the ground. Scientists now know that this design would make it impossible for dinosaurs to support their weight and walk or run with speeds estimated from the fossil record. Now it is believed that the tails served as a counterbalance. It has become commonplace to show bipeds such as Deinonychus (a Raptor such as those seen in Jurassic Park) as having a tendon-stiffened outstretched tail acting as a counterpoise and a horizontal backbone (see image). Deinonychus had a modified toe bearing a five inch sickle-shaped claw designed to gouge and slash its victims. That meant the animal had to stand on one leg while simultaneously grappling with a struggling prey. To balance like this, the rigid tail had to act like a built-in tight-rope walker's balancing pole (Desmond 77).
Compare the images of Deinonychus and the bridges. Do you see any similarites in the structures?
Activity
This activity has two parts. In the first part, students search Internet sources to develop background information. Students will list three reasons found in the sources below that support the arguement that dinosaurs carried their tails outstretched with horizontal backs. Students will cite the URL of the site in which they found their information. Next, students will assume the role of scientist. Using their newfound knowledge, they will propose a reason that they feel supports the argument about how dinosaurs carried their tails.
In the second part, students will use knowledge gained from their study of forces and weight distribution to compare a dinosaur of their choice to a bridge. Students will compare their model of a dinosaur with an outstretched tail and horizontal back to the bridge of their choice.