In our throw-away society, it just doesn't seem like kids are given the chance to really explore how things work. Yet once they start to become aware of some the basic ideas behind machines, they become excited observers, pull more things apart, and have a better appreciation the machines around them. One group of students in Joan's class, for instance, took a Walkman apart outside of class, and were excited that they could understand how two small pulley systems inside functioned, and were dependent upon a single motor. This was the kind of machine exploration and understanding that we wanted to see happen in and beyond our unit, and we have found this topic did not disappoint. Even though technologies have rapidly changed, such that many machines have even fewer visible components than the Walkman, kids still love to get their hands on planes and pulleys, as well as on tools like hammers and screwdrivers to construct and work with them.
Through writing and teaching this unit, we wanted to discuss common aspects of all simple machines, so we have tried to refer to a common language and set of concepts with the different machines we have studied. For instance, one of the most important concepts is mechanical advantage, which also helps the students to understand the value of machines. Mechanical advantage also relates to evaluating machines in class--what is the difference, for example, between whipping cream with an egg beater and a wire whisk? Work is the conceptual starting point for us in the unit. In relation to the many machines we investigate, we also emphasize friction, force, and efficiency and load, among other concepts. In general, we have written the unit so that their is a natural evolution of concepts and complexity--we move from the inclined plane to the gear, for instance, and build a conceptual relation between the two of them.
Definitely one of the kids' favorite activities was making their own pulley systems with ropes and pulleys, and lifting different weights. This activity really make the idea of mechanical advantage come to light. Another favorite was taking the kids out to explore friction, and reducing it, on the playground slide. It was surprising to see that most of the kids had never used anything to reduce their friction on the slide, and we explored different materials (including waxed paper, which really lets you fly!)
Something that we have enjoyed in this unit is that many of the activities are simple, but at the same time they are profound and intriguing. For instance, discovering levers in everyday life led us to consider and play with bats, fishing poles, tennis racquets, and golf clubs. Most of the kids caught onto how these common pieces of sports equipment effected effort and resistance.
We have learned a tremendous amount ourselves by putting this unit together and working with students to investigate simple machines. If you would like further information on the unit, or if you would like to discuss your ideas for teaching simple machines, please e-mail either Patti or Joan.
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