Structures

Opening Discussion

If the option is available to you, you should consider taking a walk in the neighborhood around your afterschool center and encouraging your students to really take notice of the buildings. Who uses these structures? What are they made of? What shapes and colors do they see? Your children may notice that the shapes most often visible in completed buildings are squares and rectangles. If you can, bring your students to a building construction site. What shapes do they see in the exposed beams?

Once back in your classroom, start the activity by having a discussion about what types of shapes they saw in buildings in the neighborhood. Ask the children which shapes they think are the strongest. You may get several different answers. Make sure to write all answers up on chart paper or a dry erase/chalk board.

The Challenge

Which is stronger: a triangle or a square? Experiment with different materials in order to discover the answer to this question.

Doing the Activity

1. Divide your children into teams of 2 or 3.
2. Give each team of students 7 of the oak tag strips and a handful of brass fasteners. Have them join the strips by inserting the brass fasteners into the holes at the ends of the strips, and have your students make 2 shapes—a shape with 3 strips (a triangle), and a shape with 4 strips (a square). Ask them to test the sturdiness of the shapes. Did the students find one of the shapes to be sturdier than the other?
3. Pass out another strip. Can any of the teams think of a way to make the 4-sided shape sturdier by adding an additional strip? Once teams have tackled this challenge, hand out more strips and let your kids experiment with any shapes they can think of.  Have the hole punches handy in case teams want to add holes to any of their strips as they experiment.

Let’s Talk About It

After 10–15 minutes of activity, stop your students and bring them together to discuss what they’ve done so far. This discussion should last no more than 5 minutes. Ask your students what they’ve discovered. Which shape is the strongest? Were they able to “stabilize” the 4-sided shape? Did they experiment with any other shapes? Go back to the board where you documented your student’s initial theories and ask them to suggest changes and additions to these theories.

Your students will find that the triangle is much sturdier than the square. This understanding is key to the later activities, in which children will build 3-dimensional shapes. When asked to stabilize the 4-sided shape, you may notice some students placing a strip diagonally across the shape, making 2 triangles. This will make the shape much sturdier. Students also may ask to add holes to the strips in an effort to make the shapes stronger—let them experiment in any way they can imagine.

Build On What They Talked About

After this brief discussion, give your students some new materials to experiment with:

1. Distribute straws and pipe cleaners to the teams. Ask each team to join 3 straws with pipe cleaners and test the strength. Then give them a fourth straw and have them make a square. Is this structure sturdy or wobbly? Do the straws follow the same rules as the oak tag?
2. Ask your students to now create the strongest 3-dimensional shape they can with the straws provided. Remind them to think about the last 2 activities. Which shape provides the most stability? Some students may have a difficult time finding a 3-dimensional shape that incorporates triangles. It is a good idea to have a model of a tetrahedron and pyramid constructed beforehand. If the teams continually create cubes, bring out the models you made. Ask the teams to explore which shape they think is stronger and allow more time for further exploration.