Understanding the science and engineering ideas about chairs as structures, why they are stable and how they possess elements that provide strength against compression and tension, can help you in teaching with this activity.

MOVIE 1 shows Goldman reviewing the concept of Center of Gravity, and demonstrating both how this can be estimated, and how its location changes when a person sits in a chair. Getting students to predict where the COG is in their own chairs, and which chair designs are stable, would show real understanding since answers concerning a new chair design cannot simply be memorized.

MOVIE 2 shows Goldman introducing orthographic projection drawings - a key tech ed goal and aspect of graphic literacy -- one science teachers typically do not pursue. Getting students to make these 3-view drawings (front, right-side and top views) can help them in communicating what their design ideas look like to others. These drawings often include measurements or dimensions so that others can build the design. It also makes scaling up a particular model chairs to half- and full-size easier.

1. How might students use words and drawings, even digital photos, to keep a record of their evolving design ideas?
2. With simple measurements noted on these drawings, what lessons related to scaling to full size could you devise?