Draft protection device design

11.B Design a solution to a problem to reduce the damage to an object in a collision (by reducing peak forces) by considering the properties of different, individual materials and shapes being used to serve particular functions.

Treat this as a pre-assessment of students’ understanding of new ideas that they will develop in the last lesson set of the unit. The first idea is related to the microscopic structure of cushioning materials. Many effective cushioning materials provide pockets or gaps of space or air between the layers of materials for the cushioner to “give”. Look for this in the second column of the design drawing. The second idea is related to how cushioners reduce peak forces in a collision. Look for students showing the protection device deforming, based on the previous work in the unit. Students will likely not show the ideas listed below, as they are ones that are new to the remainder of the unit:

• The amount of peak force is reduced because the cushioner applies a weaker force over a larger distance in a collision, which has as much effect on reducing the kinetic energy of an object as a stronger force over a shorter distance.
• These forces are transferred to both objects that the cushioner is in contact with (including the object it is protecting).
• The shape of a cushioner can be designed to distribute that force over a greater surface area, thereby reducing the amount of peak force occurring at a single location on the object being protected.

Drafting Our Protection Device Design will reveal any preconceptions about how students believe forces on the protected object can be reduced by layering certain materials. Since these ideas will be introduced in the remainder of the unit there is no need for remediation at this point. Make a copy of these explanatory models at the end of day 2 and compare them with what students show in their individual model and explanation at the end of Lesson Set 3. You may also want to have students analyze their growth by comparing these artifacts related to the ideas listed above.

Circulate to clarify student thinking. As students are drafting ideas, circulate and ask students the following questions to clarify their thinking and refine their decisions.

What shape are you using for your structure?

What is special about that shape compared to other shapes?

Would another shape work better or worse to help protect your object from damage? Why (or how)?

What constraints did you identify? Do you think your device would meet those constraints? Do you have to consider sizing or type of material?

What criteria did you identify? Can you explain on your handout how your device is able to meet that criteria?

How does your main shape and materials help meet your criteria?

What is special about that material that helps protect against damage?

How does that material react in a collision?

What other materials would function like that material? What made you choose this specific one?

How did you use those other ideas in your device design?

Can you show and explain what sets your device apart from the other devices?