Bridge Challenge

Author:

Kim Brassfield

Unit Title:

Bridge Challenge

Grade:

9

Subject:

Honors Geometry

Estimated Duration:

9 – 50 minute class periods

Unit Activities:

Date:

June 5, 2017

The Big Idea (including global relevance)

Across the entire world structures are designed and built with polygons that overlap to enhance sturdiness.

 

The Essential Questions:

Which geometric shape is used to make structures (e.g. trusses) bear the most load and ultimately be the most successful design?

Why are structures created from geometric shapes?

What is the difference between a structurally safe and unsafe bridge?

 

Justification for Selection of Content:

✓ Content is suited well for teaching via CBL and EDP pedagogies.

 

The Hook:

Students will watch a compilation of videos of bridges collapsing across the world due to not being able to withstand the load put on them or weather condition prevalent

*Possible videos:

Students will engage in a video game where they must build and design a bridge that will allow them to carry a given amount of load across it successfully.

 

 

Misconceptions:
  • Students may not view a triangle as a “strong” shape due to its slanted sides and three vertices.
  • Students may not realize that they can turn other shapes into triangles to have more support (E.g., have a square and place a diagonal through the square to create two triangles, which would mean more support for their truss).

 

The Challenge and Constraints:

 

Description of Challenge (Either Product or Process is clearly explained below):

List the Constraints Applied

Students will work in teams to design a bridge that will incorporate geometric shapes which they will randomly choose out of a basket of shape choices. They will design a bridge they feel will successfully bear a load of books. Students will test their bridge, reevaluate, redesign, and test again.

Students may only use:

  • #6 x ½” Wood screws
  • Screw drivers (75mm x 2.5mm Small Pocket Cross Philips Screwdriver)
  • Jumbo craft sticks
  • X-acto saws
  • 1” pine boards

Students have one day to build

Anticipated Guiding Questions (that apply to the Challenge and may change with student input.):
  • What is a truss?
  • What does a truss do?
  • What geometric shapes are used in building bridges?
  • What geometric shape is most commonly used in building bridges?
  • How can we measure the success of our bridge?
  • What size textbooks will we be placing on our bridge?
  • How do we measure the sum of the interior angles of a polygon?
  • Howe do we measure the exterior angles of a polygon?
  • How does the deformation of a shape affect the sum of its interior angles?
  • Is there a certain number of trusses a bridge needs?
  • What happens if just part of a truss breaks?
Engineering Design Process (EDP):

How will students test or implement the solution? What is the evidence that the solution worked? Describe how the iterative process from the EDP applies to your Challenge.

  • Students will have to build their own bridge out of wood screws and jumbo craft sticks incorporating geometric shapes.
  • Once the bridge is created, books of the same size will be placed on top of the bridge until failure (deformation of the angles of the polygons has occurred).
  • Students will measure the angles prior to the books being stacked and once the deformation has occurred and determine which types of polygons had more or less change in angle measure. This will aid in help in their redesign and rebuilding process.
  • Students will take this information, using the same material, and any type of polygons of their choice to rebuild a new bridge and retest with the same books.
  • Students should see that they used more triangles and as a result, less deformation of their bridge occurred (less change in angles or perhaps more books were able to be stacked during this iteration)

 

How will students present or defend the solution?  Describe if any formal training or resource guides will be provided to the students for best practices (e.g., poster, flyer, video, advertisement, etc.) used to present work.

Students will present or defend their solution through a “two-minute Ted Talk”.  They will be given a copy of a series of questions going through the Engineering Design Process at the beginning of the challenge to work through as they go through each step. They will be encouraged to take pictures and document as they go through the process and through both iterations of their building of their bridge. This will help them in their two-minute presentation to their classmates.

 

What academic content is being taught through this Challenge?

  • CCSS.Math.Content.HSG-MG.A.3: Apply geometric concepts in modeling situations
    Apply geometric methods to solve design problems (e.g., designing an object or structure to satisfy physical constraints or minimize cost; working with typographic grid systems based on ratios).
  • CCSS.Math.Content.HSG-MG.A.1: Use geometric shapes, their measures, and their properties to describe objects (e.g., modeling a tree trunk or a human torso as a cylinder)
  • CCSS.Math.Content.G.CO.14: Classify two-dimensional figures in a hierarchy based on properties.
  • CCSS.Math.Content.7.G.1: Solve problems involving similar figures with right triangles, other triangles, and special quadrilaterals.

 

ACS (Real world applications; career connections; societal impact):

Real world applications:

This challenge is strongly real world related during to the fact that just about every structure in the world is created using geometric polygons and is composed primarily of triangles due to their angular integrity and; therefore, an ability to hold a heavy load.

 

What activities in this Unit apply to real world context?

The challenge

 

Societal Impact:
 

­­­­­­­­­­­­­­The concepts in this unit have a societal impact being that many objects, structures, etc. are built and reinforced with triangles and many other polygons due to their structural integrity. Students will be able to see this in their community and when they travel across the world.

 

What activities in this Unit apply to societal impact?  

The challenge

 

Careers:  What careers will you introduce (and how) to the students that are related to the Challenge? (Examples: career research assignment, guest speakers, fieldtrips, Skype with a professional, etc.)

  •  The hook and discussion that follows will shed light on what civil engineers must take in to consideration when designing a bridge.
  • In addition, when building and testing their bridge during the challenge, students will act as civil engineers and follow the engineering design process to create and test their bridge under compressive load.

 

Unit Academic Standards:
Next Generation Science Standards (NGSS):

Science and Engineering Practices:

 
 
Crosscutting Concepts:
 
 
Ohio’s New Learning Standards for Science (ONLS):

 

Ohio’s Learning Standards for  Math (OLS) or Common Core State Standards -- Mathematics (CCSS)

☒ Make sense of problems and persevere in solving them

☒ Construct viable arguments and critique the reasoning of others

☒ Model with mathematics

☒ Use appropriate tools strategically

☒ Attend to precision

☒ Look for and make use of structure

☒ Look for and express regularity in repeated reasoning

 

Post Implementation- Reflection on the Unit:

All students showed growth from the pre- to post-test for this unit.  In addition, I teach three Honors Geometry classes, I only completed this unit in one of them. This Honors Geometry class’s chapter test average was higher than the other two which is also evidence of student growth and understanding of this material. Also, students had to use protractors to measure the angle of deflection after their truss was tested. In a later activity, that all three of my geometry class participated in, this skill seemed to be heightened in the class I did my CEEMS practice in due to the additional practice in a real-life setting.

Lastly, it was observed, a student aspiring to be an engineer, who does minimal work and rarely does traditional learning activities in our classroom, really excelled and was motivated to work throughout this entire unit which is not normally evident on a daily basis.

Students did a great job with their initial sketches; however, as the first day of building began we quickly ran into a hurdle as the ease of drilling a hole into a popsicle stick with a screw driver was extremely difficult. For this reason, I took the popsicle sticks home and drilled them in 5” increments (I would do this beforehand next time or bring it student’s own hand drills for them to drill themselves. I would also give them screwdrivers with longer handles. If a teacher implanting this unit plans to use hand drills – I would be sure that the school had access to at least enough for 2 per group and would also be sure that the students know how to use these tools prior to the lesson beginning). The building process, in general, took a lot longer than the one day allotted – it took three. As a result, I did not have enough time for students to rebuild as desired; instead they simply resketched.

Another error that occurred is two groups decided to quickly begin testing before getting approval from me. For this reason, I will be sure to have “sign off” section on this part of the EDP packet next year. I will also be sure that everyone is clear of the testing objective prior to the testing phase. Students thought the objective was to see how much load (aka books) their truss could handle until failure; however, I did not want them to fail – they were to add load until angle deformation (slight change) occurred.

Overall, through those errors there was a lot of engagement and learning that took place and I would do this project again – but, try to think of a way to incorporate more of our standards from Ch. 6 – where the standards already in place in this unit came from. I have some generalized ideas on how to approach this: instead of students testing to show the strength of triangles, they would instead test the properties of various quadrilaterals and determine which properties impact the truss the most. The essential question would be more open-ended, “How do geometric shapes influence structural design?” Students would have to learn the properties of the quadrilaterals first to be able to know what to test and; therefore, the unit would take place at the end of the chapter versus toward the beginning.

 

Pre Test
Post Test
 

Additional Resources: