# Hands-on ActivityForces in Structures: Glue Sticks Bend & Twist

### Quick Look

Time Required: 15 minutes

Expendable Cost/Group: US \$0.25

Group Size: 2

Activity Dependency: None

Subject Areas: Physical Science

### Summary

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

### Engineering Connection

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

### Learning Objectives

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

### Educational Standards Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards. All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org). In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.

###### International Technology and Engineering Educators Association - Technology
• Refine design solutions to address criteria and constraints. (Grades 6 - 8) More Details

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###### Massachusetts - Science
• Explain how the forces of tension, compression, torsion, bending, and shear affect the performance of bridges. (Grades 6 - 8) More Details

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### Materials List

• glue sticks (the kind used in heated glue guns)
• rulers (for measuring)
• thin permanent markers (for marking on the glue sticks)

### Introduction/Motivation

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).

### Procedure

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.

### Assessment

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

### Investigating Questions

• 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?

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### References

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