# 9.1: Unit Overview and Content Focus

This unit focuses on the concepts of stress, strength, deflection, point of failure, allowable strength, bending strength, and factor of safety. To model these concepts in action and allow the students to conduct their own tests, the experiment tests the strength of popsicle sticks of varying sizes. The strength of a material is defined as the amount of stress that causes failure. Failure occurs when the stress is larger than the strength, causing the popsicle stick to break under the given load (weight). Once the basic concepts of strength of materials are understood, the students are tasked with an engineering project, the designing of a bridge that can withstand a maximum amount of stress before failing. The students test their designs using a computer-based bridge building simulation, make necessary modifications, and then construct the actual bridge using popsicle sticks and glue. The bridges are tested by the teacher to determine their strength.

^{*}The entire unit is composed of four smaller lessons that can be utilized individually or together as part of a larger project.