Bronxville High School students launched marbles, erasers and tennis balls with their handmade trebuchets as part of a culminating project in Kevin Geidel’s Advanced Placement Physics class.
“This project was about the flow and transformation of mechanical energy,” Geidel said. “Students were expected to develop mathematical models, using energy analysis and kinematics, to describe the way their planned trebuchet would work. Once built, they took experimental data from the physical model and compared their results to what their equations predicted would happen.”
Applying their knowledge of forces, energy transfer and motion, each student worked independently to design their project, using a variety of materials and tools. They began the process by creating a scaled drawing of what they intended to build and annotated their diagrams to demonstrate the flow of energy. Having studied kinematics, they made predictions about the speed, energy, height and range of the projectile as it was launched and used their calculations to predict the mechanical power output of their trebuchets.
“Once their device was built, they filmed it launching a projectile,” Geidel said. “They used motion-tracking video analysis to measure the time it took to launch, the initial speed of the projectile, initial launch angle, the maximum height the projectile reached and the distance the projectile traveled. Then, the students used the same energy analysis and kinematics to first calculate how efficient their trebuchet actually was.”
Geidel said the project encouraged the students to work independently and think critically, while some students tweaked their designs throughout the trial-and-error process.
“The students rolled up their sleeves and got to work,” Geidel said. “The results were incredible. I am very proud of them. They have built a wealth of knowledge over the course of the year so far, and they generate thoughtful, viable solutions when they apply themselves.”
In their final reports, the students reflected on how their trebuchets worked and the motivation behind the design choices. They also discussed performance specifications and included proposals on how to scale up their designs.