In this ten-day project the students should learn how to apply abstract concepts, such as stress, fulcrums, the law of gravity, and the strength of different geometric shapes. Working in cooperative groups of four, student contractors operate simulated architectural firms to create strong, economical bridges and account for construction costs. The construction team of four students will design and build a model bridge of wooden toothpicks from specifications given in the contest rules and code. The construction teams must also keep schedules, inventory records and balance sheets of costs. Each model toothpick bridge will be evaluated and judged for economy of design, neatness, and accuracy (that is, how well they match their plans) before they are judged for strength. The length of time to accomplish this lesson is up to ten 45-minute class periods.
ITV Series
Landscape of Geometry:Trussworthy (TV Ontario)
Students will be able to:
(classroom)
Vocabulary:
truss -- a framework of triangles that distribute the weight outward and gradually down instead of straight downroadbed -- the part of the bridge people and vehicles travel on
abutment-- the supports at each end of the bridge
beam bridge -- flat across and supported at the two ends
arch bridge -- this bridge has an arch shape below or above the deck
suspension bridge-- a roadway hanging by cables from two or more towers
(Most of the vocabulary will be visual, and will be introduced with the photographs of the bridges.)
Landscape of Geometry is a series of eight segments that relate how applied geometry is used to solve problems in the world around us.
Give each student a piece of drawing paper. Ask the students to draw a bridge. Hang these drawings around the classroom. Start a discussion on what they observe when they look at their classmates' drawings (similiarities and differences).
Show some poster-size pictures of six famous bridges such as The Golden Gate or The Verrazano-Narrows. Have the students identify the kind of bridge, the name of the bridge and why it was built. Identify what geometric shapes are used most frequently in these particular bridges. (This would be part of the second of ten lessons. Students have already researched the history of bridges and the types of bridges in the first lesson.)
Arrange the class into construction teams of four. Give each team fifteen photographs of bridges in their community. Each team will list the location of each bridge (may give landmarks), identify the type of bridge and the purpose of the bridge.
The focus for viewing is a specific responsibilty or task(s) students are responsible for during and after watching the video to focus and engage students' viewing attention. To give students a specific responsibilty while viewing the video say, "When the video begins, listen and look for the geometric shape that is commonly used in bridge designs. Find out why it is used in bridge building and the name of this design."
Start the video where the host, David Stringer says, "It's easy to make shapes that are sloppy..." (He is holding a sloppy geometric shape that collapses.)
Stop the video after David Stringer says, "...used everywhere to build large structures." Ask the students to name the geometric shape that is commonly used in bridge building. (triangle) Do the activity called Truss Design. (Refer to handout.) Give each team eight strips of cardboard and seven paper fasteners. Follow the directions to show what geometric shape gives bridges and buildings their strength.
Refocus on the video by asking the students to find a method used in ancient societies to assure that a bridge stays up and a method from the present to assure its strength. (In the past, they would bury human sacrifices under the foundation of the bridge to make the gods happy so the bridge would not fall down. Fortunately, today we use geometry.) Resume the video where David Stringer is walking down a bridge saying, "It wasn't always that way,you know."
Pause the video after David Stringer says, "Lucky for us today's bridge builders use geometry and not human sacrifices to make the bridges stay up." Ask the students for a method from the past and the present used to construct bridges that remain standing.
Say, "Let's resume the video to find the meaning of truss and how it is used in building bridges."
Pause the video after David Stringer says, "...can be used to span long distances." (He's standing on a truss.) Ask the students for the meaning of truss and why it's used so often in building bridges.
Say, "Let's resume the video to find out other uses of trusses and why builders choose one shape over another."
Stop the video after David Stringer says, "Happy hunting."
To reinforce the strength of a triangle, the use of the truss design in bridge building and to practice creating your own design, each construction team will make a practice bridge from straws and pipe cleaners.
Instruct the students to make a sketch of their bridge design on centimeter graph paper or sketch paper. (Bridge cannot be longer than 35 cm or wider than 6 cm.) Make sure everyone as a team agrees on the design.
Using only straws and pipe cleaners, each team will begin to construct their bridge. They may cut straws and pipecleaners to any size.
Say, "In approximately twenty minutes, we will test the bridges for strength. The weights will be books (each book will be of the same weight). The books will be stacked one at a time on the top middle part of the bridge. You will keep stacking books until the bridge collapses."
After all the bridges have collapsed, and weights and maximum loads have been recorded, have the students calculate the efficiency of their bridge. (Refer to the Engineering Efficiency handout.)
Arrange to have a local engineer talk to the class about bridge building. In our particular town, two bridges were recently reconstructed.
The engeering firm could share with the class the process of reconstructing a bridge, along with visiting the actual bridges.
Take a trip to the nearest city and have the students photograph buildings and bridges. Discuss the designs and the uses of various geometric shapes.
Working with the town's Parks and Recreation Supervisor, find a location where the students can apply their bridge building knowledge to constructing an actual footbridge. The students will check the site for the footbridge and make decisions as to the size, design and materials needed to construct this bridge. Going through the proper chain of commands and using the community's resources (parents, housebuilding contractors, carpenters, hardware stores, lumber yards, etc.), the students will assist in the actual construction of their footbridge.
Work on designing buildings through the use of the software Elastic Lines and Corel Draw.
Social Studies/Language Arts: Have students research and discuss: How have bridges between nations affected our history? the use of language? the development of societies throughout history? Read The Bridge Book by Polly Carter.
Science: Discuss past, present and future scientific theories and advancements, and how they apply to bridges and bridge building.
Discuss Newton, and his laws of motion and how they apply to the model bridges' efficiency.
Jeanne Pollard, Building Toothpick Bridges, Dale Seymour Publications,1985,.
Teaching with Model Bridge Building Programs, Midwest Products Co., Inc. 1986.
Polly Carter,The Bridge Book, Simon&Schuster, 1992.
How Do They Build Bridges?, Popular Mechanics for Kids, 1996, The Hearst Corporation.