As an introduction to bioengineering, student teams are given the engineering challenge to design and build prototype artificial limbs using a simple syringe system and limited resources. As part of a NASA lunar mission scenario, they determine which substance, water (liquid) or air (gas), makes the appendages more efficient.

Students learn about stress and strain by designing and building beams using polymer clay. They compete to find the best beam strength to beam weight ratio, and learn about the trade-offs engineers make when designing a structure.

In this math activity, students conduct a strength test using modeling clay, creating their own stress vs. strain graphs, which they compare to typical steel and concrete graphs. They learn the difference between brittle and ductile materials and how understanding the strength of materials, especially steel and concrete, is important for engineers who design bridges and structures.

Students explore how tension and compression forces act on three different bridge types. Using sponges, cardboard and string, they create models of beam, arch and suspension bridges and apply forces to understand how they disperse or transfer these loads.

Students are presented with a brief history of bridges as they learn about the three main bridge types: beam, arch and suspension. They are introduced to two natural forces tension and compression common to all bridges and structures. Throughout history, and today, bridges are important for connecting people to resources, places and other people. Students become more aware of the variety and value of bridges around us in our everyday lives.

Students identify different bridge designs and construction materials used in modern day engineering. They work in construction teams to create paper bridges and spaghetti bridges based on existing bridge designs. Students progressively realize the importance of the structural elements in each bridge. They also measure vertical displacements under the center of the spaghetti bridge span when a load is applied. Vertical deflection is measured using a LEGO MINDSTORMS(TM) NXT intelligent brick and ultrasonic sensor. As they work, students experience tension and compression forces acting on structural elements of the two bridge prototypes. In conclusion, students discuss the material properties of paper and spaghetti and compare bridge designs with performance outcomes.

Students create and analyze composite materials with the intent of using the materials to construct a structure with optimal strength and minimal density. The composite materials are made of puffed rice cereal, marshmallows and chocolate chips. Student teams vary the concentrations of the three components to create their composite materials. They determine the material density and test its compressive strength by placing weights on it and measuring how much the material compresses. Students graph stress vs. strain and determine Young's modulus to analyze the strength of their materials.

Students work in pairs to create three simple types of model bridges (beam, arch, suspension). They observe quantitatively how the bridges work under load and why engineers use different types of bridges for different places. They also get an idea of the parts needed to build bridges, and their functions. The strength of model bridges is mainly a factor of the quality of materials used, and therefore they do not provide a clear visual representation of tension and compression forces involved. Yet, students are able to see these forces at work in three prototype designs and draw conclusions about their dependence on span, width and supporting structures of the bridge designs.

Students learn about nanocomposites, compression and strain as they design and program robots that compress materials. Student groups conduct experiments to determine how many LEGO MINDSTORMS(TM) NXT motor rotations it takes to compress soft nanocomposites, including mini marshmallows, Play-Doh®, bread and foam. They measure the length and width of their nanocomposite objects before and after compression to determine the change in length and width as a function of motor rotation.

Students learn about the types of possible loads, how to calculate ultimate load combinations, and investigate the different sizes for the beams (girders) and columns (piers) of simple bridge design. Students learn the steps that engineers use to design bridges: understanding the problem, determining the potential bridge loads, calculating the highest possible load, and calculating the amount of material needed to resist the loads.

Students are introduced to the five fundamental loads: compression, tension, shear, bending and torsion. They learn about the different kinds of stress each force exerts on objects.

Working individually or in groups, students explore the concept of stress (compression) through physical experience and math. They discover why it hurts more to poke themselves with mechanical pencil lead than with an eraser. Then they prove why this is so by using the basic equation for stress and applying the concepts to real engineering problems.

Through a series of three lessons, each with its own hands-on activity, students are introduced to 1) forces, loads and stress, 2) tensile loads and failure, and 3) torsion on structures—fundamental physics concepts that are critical to understanding the built world. The associated activities engage students through experimenting with hot glue gun sticks to experience tension, compression and torsion; the design of plastic chair webbing strips; and problem-solving to reinforce foam insulation "antenna towers" to withstand specified bending and twisting.

Students conduct several simple lab activities to learn about the five fundamental load types that can act on structures: tension, compression, shear, bending and torsion. In this activity, students play the role of molecules in a beam that is subject to various loading schemes.

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

Using spaghetti and marshmallows, students experiment with different structures to determine which ones are able to handle the greatest amount of load. Their experiments help them to further understand the effects that compression and tension forces have with respect to the strength of structures. Spaghetti cannot hold much tension or compression; therefore, it breaks very easily. Marshmallows handle compression well, but do not hold up to tension.

Students learn about how biomedical engineers create assistive devices for persons with fine motor skill disabilities. They learn about types of forces, balanced and unbalanced forces, and the relationship between form and function, as well as the structure of the hand. They do this by designing, building and testing their own hand "gripper" prototypes that are able to grasp and lift a 200 ml cup of sand.

Students take a hands-on look at the design of bridge piers (columns). First they brainstorm types of loads that might affect a Colorado bridge. Then they determine the maximum possible load for that scenario, and calculate the cross-sectional area of a column designed to support that load. Choosing from clay, foam or marshmallows, they create model columns and test their calculations.

Students are introduced to the field of biomechanics and how the muscular system produces human movement. They learn the importance of the muscular system in our daily lives, why it is important to be able to repair muscular system injuries and how engineering can help.

Students take a close look at truss structures, the geometric shapes that compose them, and the many variations seen in bridge designs in use every day. Through a guided worksheet, students draw assorted 2D and 3D polygon shapes and think through their forms and interior angles (mental “testing”) before and after load conditions are applied. They see how engineers add structural members to polygon shapes to support them under compression and tension, and how triangles provide the strongest elemental shape. A PowerPoint® presentation is provided. This lesson prepares students for two associated activities that continue the series on polygons and trusses.