To explore the nature of systems by examining the systems that make a bicycle work. Students will begin to understand how the different systems of a bicycle relate to each other and be able to identify the properties of each part or subsystem.
This lesson gives students an opportunity to examine the nature of systems in the context of an object with which they are very familiar – the bicycle. While this lesson is intended for grades 6-8, it presents concepts that are more appropriate for 7th and 8th grade students.
The main goal of having students learn about systems is not to have them talk about systems in abstract terms, but to enhance their ability (and inclination) to identify the various aspects of systems in attempting to understand the whole system. Examining systems is really a way of thinking rather than theories or discoveries.
Students will identify the properties of the various subsystems of a bicycle and examine how they relate to the whole. According to research: “Children tend to think of the properties of a system as belonging to individual parts of it rather than as arising from the interaction of the parts. A system property that arises from interaction of parts is therefore a difficult idea.” (Benchmarks for Science Literacy, p. 262.)
Students should already know that if something consists of many parts, the parts usually influence one another. Also they should be aware that something may not work as well (or at all) if a part of it is missing, broken, worn out, mismatched, or misconnected.
It is important to establish the boundary of the system to include enough parts so that their relationship to one another makes sense. Drawing the boundary of a system well can make the difference between understanding and not understanding what is going on. Thinking of everything within some boundary as being a system suggests the need to look for certain kinds of influence and behavior. For example, students should consider a system’s inputs and outputs-the outputs of some parts being inputs for others.
Systems are not mutually exclusive. Systems may be so closely related that there is no way to draw boundaries that separate all parts of one from all parts of the other. Any part of a system may itself be considered as a system-a subsystem-with its own internal parts and interactions. Any system is likely to be part of a larger system that it influences and that influences it. The idea of a system should be expanded to include connections among systems.
Students will also learn about the choices and constraints that go into the design of a bicycle system. Depending on whether the bicycle is intended for racing, mountain roads, or touring, influences its design and such choices as the type of tires, frame and materials, and drives and gears. In addition, accommodating one constraint can often lead to conflict with others. For example, the lightest material may not be the strongest, or