Strength From Shape

In Nature Does Shape Matter?

There are all sorts of different shapes and patterns that one can see in nature. Most are not at all random, but have been developed and refined over billions of years of natural selection. They have also been shaped by physical forces like gravity or surface tension.  Successful shapes have survived because they serve a function. One benefit of a successful shape is that it saves material while still doing its job, whether that's holding up leaves to sunlight or anchoring a muscle to a flapping wing, or containing the liquid within a cell. Less material means the organism expends less energy growing, and less energy carrying the weight. Some of the most elegant shapes in nature are those that have to be both strong and light. These are forms that possess strength from shape.

In this lesson students are shown several artifacts illustrating strength from shape: bird breast bone, seed pods, scallop shell, etc., and are asked what other examples they can think of, why they are good examples, do they think there are recurring geometries to the shapes, and how they think the material got that way.

A short lecture introduces the basics of physics of forces that might be acting on the organisms: compression, tension, torque. Students are then shown a demonstration of how the same material can be stronger or weaker depending on the shape that it is formed into: can a card stock sheet hold up a brick? Yes, it can, if it is folded into an accordion and formed into a cylinder.

Finally, the class is divided into competing teams and given a design challenge that requires them to use shapes to create strength. You can download an overview of the lesson and an educator's guide by going to the attachment section (requires site registration and login).