A Stable Table
|Level: Beginner||Duration: 20-30 minutes|
|Grade Level:||Author: Adapted from Brick Layers II|
|Topics: Structures, Polygons|
|Materials: LEGO Bricks Set|
|References / Resources:|
Students will build polygons and test them to see which ones are stable.
Students will explore the structural properties of various polygons, including the triangle, pentagon, heptagon, and more!
The names of the polygons in the activity are: Triangle (3 sides), Quadrilateral (4), Pentagon (5), Hexagon (6), Heptagon (7), and Octagon (8).
The triangle is the only polygon that is intrinsically stable (does not change shape). If one vertex is moved, all its other vertices must move with it. The length of one side cannot be changed without changing at least one of the others. This unique stability makes the triangle very useful in construction. It is used to form stable structures and to reinforce unstable shapes.
- Discuss the key question: What polygons can be used to make a stable structure?
- Ask students to take three beams and connector pegs to form a triangular shape.
- Have them place the structure so it lies on the table. Tell them to hold one of the beams securely to the table while they push and pull on the shape to determine if it is stable (does not change shape).
- Direct the students to record the number of sides, the name of the polygon, and if it is stable or unstable.
- Have the students repeat this procedure after adding another beam to the polygon. Have them continue adding beams until they have completed the octagon. (The polygons formed may not be regular if different lengths of beams are used.)
- Which polygons are stable? [triangles]
- Which polygons are not stable? [all but the triangle]
- If you were going to make a structure and did not want it to be unstable and move, what polygons would you use in your construction? [triangles]
- Explain in your own words why you think triangles are stable.
- Where have you seen triangles used to make structures more stable?
- Have students make a list of different structures they observe around them. Have the students identify the geometric shapes and make inferences as to why the structure is made with this shape.
- Have students explore ways to make unstable polygons stable.