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Students use hot glue gun sticks to learn about the forces of tension, compression and torsion.

Engineers consider the impact of forces when designing and creating structures. bending compression force shear tension torsion twist Students demonstrate their knowledge of compression, tension and torsion by conducting the experiment and successfully answering follow-up questions. glue sticks (the kind used in heated glue guns) rulers (for measuring) thin permanent markers (for marking on the glue sticks) 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 student follow the procedures outlined below: 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. Holding the glue stick between a finger and thumb, apply a force to the middle and note how the lengths and shapes of the lines change. Use a ruler to mark a series of straight lines along the length of a glue stick, as described in the previous experiment. 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. What happens to the line on the top of the glue stick (the side where your finger pushes)? What happens to the line on the bottom? What happens to the lines on the two sides of the glue stick? What is tension? Compression? What happens to the lines on the glue stick when it is twisted? Imagine that each vertical line represents a line of glue molecules. Notice how they have been slid sideways out of position by the twisting movement. This is the sign of shear forces acting inside the material. Can you explain shear force? What is torsion? Assign the Investigating Questions as homework or a quiz. Or conduct a class discussion. (Refer to associated lesson for background information on forces.) PBS Building Big - Forces Lab Forces Lab