Last month Paul Revere eighth grade science teacher Robert Aochi assigned his students a unique project: design the strongest, lightest model bridge possible using only quarter-inch balsa wood, glue and creativity. Their bridges were then tested in a structural stress machine used by many engineering schools. Aochi wanted his students to actually be able to see the physics concept of force in action. By applying weight to their finished bridges, the students could see the importance and practicality of engineering as related to construction. The bridges were scored in two ways: the amount of weight a structure held and the ratio of weight-bearing to bridge mass. The highest scoring bridge held 147 pounds and weighed in at 92.1 grams. It was built by Camille Wada, Nick Sinclair, Laura Johnson and Ryan Legaspi. In second place at a weight of 119 pounds and mass of 51.7 grams was the bridge designed by Elizabeth Silvers, Shelby Pascoe and Kimberly Cronin. Richie Meade-Miller, Renee Park, Daniel Makabeh and Tony Adlcedo built and designed the top-scoring bridges for weight-bearing to bridge mass with a score of 1,117.98. Their bridge weighed 46.7 grams and held 115 pounds. In second place with 1,108 was Adam Levin, Kevin Schilling, Kene Izuchukwu, Jason Rahimian and Daniel Melgerai’their bridge weighed 46.3 grams and held 113 pounds. The bridge-building project also accomplished Aochi’s other objectives, including promoting group cooperation, long-term organizational skills, problem-solving and stressing the importance of science/technology in today’s society. “Some kids are good at textbook learning and others are good at design and craftsmanship,” Aochi said. “The bridge project works towards everyone’s strengths.” Students in Aochi’s class was allowed to choose their own group. The groups were required to get together over the three-week winter vacation to research, design and build a model bridge. In addition to the constructed bridge, they had to turn in a scaled plan of the dimensions of the bridge and a written report on a three-sided display board. The written report had to include the history of bridges, structural types and what forces are involved. The only materials allowed on the finished project were balsa wood and glue’no pins or gussets (brackets strengthening an angle of a structure) were allowed. “They’d weigh too much anyway,” Cronin said. The maximum weight for the finished bridge was 95 grams. The students were required to work within a maximum length of 40 cm., width of 10 cm. and height of 21 cm. The minimum span was 25 cm. and the minimum clearance was 10 cm. The bridges constructed with those dimensions could fit into a large shoe box. The rules for the bridge also included specific rules for joint assembly, and all the angles supporting the span had to be larger than 30 degrees. “I can’t believe how much the bridge supported,” said Martha Meade, mom of eighth grader Richie. “When you think about how they put it together with balsa wood, it’s amazing! It was a great project.” “Some groups were really motivated; They liked building and testing their ideas,” Aochi said. “Other groups focused on each team member’s strengths, whether it was research, project design or model-building. If we had had more time, we would have let each team try to redesign it and improve on their bridge once they had seen the bridge’s weak spot.” He admitted he’s often as surprised as the students with the result of the stress test. “Sometimes you can tell students put a lot of work into the design and it only holds 25 pounds,” he said. “The same students see another group with a bridge that looks like it’s been hastily put together and it holds a lot more.” Aochi graduated from USC with a B.A. in biology and has taught at Revere for 24 years. He enjoys the enthusiasm of eighth graders as he introduces different concepts. “We have a lot of fun discussing questions such as ‘If the earth is moving and you’re moving, are you really moving?'” Aochi said, explaining, “It’s all relative; it depends on your reference point.” Eighth graders at Revere study physics, chemistry and astronomy. Aochi’s students have already designed wind cars, roller coasters and bridges. In the near future, they’ll have ice cream lab in chemistry, where they’ll learn heat exchange. “For a lot of kids this is their first introduction to chemistry and physics concepts,” Aochi said. “By doing projects it becomes more real for them.”
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