Forces in Structures: Glue Sticks Bend & Twist

Engineers consider the impact of forces when designing and creating structures.

Students demonstrate their knowledge of compression, tension and torsion by conducting the experiment and successfully answering follow-up questions.

When structures are being built, engineers must be aware of the forces that will be acting on the structure --- so they can make appropriate design and materials decisions. In today's activity, we will investigate those forces and how they might affect a structural member (a glue stick).

Have students follow the procedures below:

Glue stick experiment to show tension and compression created by bending.

1. Use a ruler to mark four straight 4-inch lines that run the length of a glue stick. Space the lines 90-degrees apart: one on the top, one on the bottom, and one on each side of the glue stick.
2. Holding a glue stick between a finger and thumb, apply a force to the middle and note how the lengths and shapes of the lines change.

Glue stick experiment to show torsion.

1. Use a ruler to mark a series of straight lines along the length of a glue stick, as described in the previous experiment.
2. Have pairs of students work together: Have one student hold one end of the glue stick, while his/her partner twists the other end as hard as possible.

Assign the Investigating Questions as homework or a quiz. Or conduct a class discussion. (Refer to associated lesson for background information on forces.)

Forces Lab. Building Big. PBS. http://www.pbs.org/wgbh/buildingbig/lab/forces.html