Ideas in Motion

Third Grade Construction Engineers and Architects

The challenge for third graders:  construct a three-dimensional structure sturdy enough to stand up on its own without leaning against anything or using anything for support. It must be large enough so that you can fit completely inside!

Materials available: rods made from straws, newspaper, tape

Grady’s Project

My 3-D shape is a pentagonal prism with a pentagonal pyramid on top. I had previously planned to make a cube, but after I had built it I realized it couldn’t stand up on its own. I finally decided on a pyramid since they lean inward and they’re very sturdy because of that.
 
On this try, I cut off the ends of the rods that I was using. Since they are made of newspaper, a drinking straw, and some tape, they’re very vulnerable to bending—especially the ends. I had finished my pentagonal pyramid, but realized that it was too small for me to fit in! I decided to put a pentagonal prism underneath the pyramid, but when me, my grandfather, and my little brother Thomas stuck the pyramid on top of the prism, the 5 rods that pointed upward on the prism buckled and folded, making the prism spin and descend, so now all I had was a collapsed prism-pyramid.
 
My mother had the idea of putting smaller rods on the 5 upward rods as well as the horizontal pieces by putting them at an angle (about 45 degrees).  This made triangle shapes in the corners to support the weight of the pyramid, and so I did that with some help from her and Thomas, and there was my 3-D shape! It has 11 faces—5 triangular, 5 rectangular, and 1 pentagonal. It was 20 edges and 11 vertices. It has 20 rods total in it.