Then using a box of recycled cardboard and paper, tape, wire, and string, the girls had to a build a bridge that would hold 50 pennies.
A most fun part of the exercise was listening to them decide to build a single and then work together to come up with design ideas. There was quite a bit of negotiation that had to take place! They created a design board and then noticed and discussed the pros and cons of each design. They narrowed it down to two they thought would be most sturdy and asked me to choose. I liked them both and set them to the task of seeing which was stronger.
And then we tested the strength of the bridge by adding 50 pennies to the deck.
Both held up but buckled in the center so we discussed how they could have strengthened the bridges and one determined she needed more tension and the other decided she needed one additional support.