Building, Part 2: Creating Shapes and Toothpick Trusses

2-D to 3-D
Predicting what 3-dimensional shape might be formed when a 2-dimensional pattern was cut out and folded along dotted lines.

Exploring faces and vertices. They discovered that both the tetrahedron and the pyramid have four triangular faces but that the pyramid also has a square base as its fifth face.

Making structures out of toothpicks and gumdrops.

Which shape is more stable, a triangle or a square?
We learned that triangles made structures more stable because they formed a truss, which is a skeleton-like structure composed of struts, some of which are in compression and some in tension, which are joined to form a series of triangles.
First we built all the same shapes that we had just made with paper using gumdrops and toothpicks this time.
Then we began building a bridge with trusses by constructed a rectangular box of toothpicks and gumdrops. We tested its stability by pressing down on it and wiggling it and found it not so stable.
Next I challenged them to add more materials to strengthen the box. They added cross-pieces and triangular braces. They then extended their trusses to see how wide a gap they could make that still could be stable.

We looked at pictures of bridges which had trusses, which connected what they were learning to real-life situations. After the lesson, I let them go whichever way they wanted to with the materials and they had a wonderful time being creative and their structures just kept on growing!
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