This four-minute video clip highlights the re-creation of a medieval trebuchet, a device used to launch large projectiles. It gives a close-up look at the design process, beginning from small physical models and ending with a massive device that hurls a piano. Kids will gain a deeper understanding of the mechanical advantage of levers and the importance of modeling a process before implementing a design (the first model was wobbly and dangerous). The concept of potential and kinetic energy is also explicitly addressed in the video.
6-8: 3B/M4b. The most common ways to prevent failure are pretesting of parts and procedures, overdesign, and redundancy.
9-12: 3B/H6. To reduce the chance of system failure, performance testing is often conducted using small-scale models, computer simulations, analogous systems, or just the parts of the system thought to be least reliable.
3C. Issues in Technology
6-8: 3C/M3. Throughout history, people have carried out impressive technological feats, some of which would be hard to duplicate today even with modern tools. The purposes served by these achievements have sometimes been practical, sometimes ceremonial.
4. The Physical Setting
4E. Energy Transformations
6-8: 4E/M4. Energy appears in different forms and can be transformed within a system. Motion energy is associated with the speed of an object. Thermal energy is associated with the temperature of an object. Gravitational energy is associated with the height of an object above a reference point. Elastic energy is associated with the stretching or compressing of an elastic object. Chemical energy is associated with the composition of a substance. Electrical energy is associated with an electric current in a circuit. Light energy is associated with the frequency of electromagnetic waves.
9-12: 4E/H1. Although the various forms of energy appear very different, each can be measured in a way that makes it possible to keep track of how much of one form is converted into another. Whenever the amount of energy in one place diminishes, the amount in other places or forms increases by the same amount.
9-12: 4E/H9. Many forms of energy can be considered to be either kinetic energy, which is the energy of motion, or potential energy, which depends on the separation between mutually attracting or repelling objects.
6-8: 4F/M3a. An unbalanced force acting on an object changes its speed or direction of motion, or both.
8. The Designed World
8B. Materials and Manufacturing
6-8: 8B/M2. Manufacturing usually involves a series of steps, such as designing a product, obtaining and preparing raw materials, processing the materials mechanically or chemically, and assembling the product. All steps may occur at a single location or may occur at different locations.
11. Common Themes
6-8: 11A/M2. Thinking about things as systems means looking for how every part relates to others. The output from one part of a system (which can include material, energy, or information) can become the input to other parts. Such feedback can serve to control what goes on in the system as a whole.
6-8: 11B/M6. A model can sometimes be used to get ideas about how the thing being modeled actually works, but there is no guarantee that these ideas are correct if they are based on the model alone.
9-12: 11B/H5. The behavior of a physical model cannot ever be expected to represent the full-scale phenomenon with complete accuracy, not even in the limited set of characteristics being studied. The inappropriateness of a model may be related to differences between the model and what is being modeled.
PBS Learning Media: Energy Transfer in a Trebuchet. (n.d.). Retrieved March 3, 2015, from WGBH Educational Foundation: http://www.pbslearningmedia.org/resource/hew06.sci.phys.maf.trebuchet/energy-transfer-in-a-trebuchet/
WGBH Educational Foundation. PBS Learning Media: Energy Transfer in a Trebuchet. Boston: WGBH Educational Foundation. http://www.pbslearningmedia.org/resource/hew06.sci.phys.maf.trebuchet/energy-transfer-in-a-trebuchet/ (accessed 3 March 2015).
PBS Learning Media: Energy Transfer in a Trebuchet. Boston: WGBH Educational Foundation. 3 Mar. 2015 <http://www.pbslearningmedia.org/resource/hew06.sci.phys.maf.trebuchet/energy-transfer-in-a-trebuchet/>.
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