Fourth-Grade Lesson Plans on Simple Machines
Simple machines are the simplest systems or devices for using mechanical advantage (essentially, leverage) to change the magnitude or direction of a force. The six simple machines defined by Renaissance scientists are the lever, wheel and axle, pulley, inclined plane, wedge and screw. Exploring simple machines can be a great way to help your fourth-grade pupils understand concepts relating to force and work.
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Levers
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Start by giving the pupils a list of the terms they'll need to understand (for example load, fulcrum and effort) so that they can research them. They should be able to describe what a lever is and what it's used for, and give examples of levers in everyday use. Your pupils' practical experiments will consist of using long rulers as levers and lifting different loads, positioning the fulcrum and load at varying distances along the ruler and noting the effects.
Gears
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Your pupils will first familiarize themselves with what gears are (toothed wheels that mesh together) and what they can do (transmit turning force, change the amount of force, change the speed or direction of rotation, and synchronize the rotation of different axles). Your pupils will learn about gear ratios (the relative numbers of teeth on gears in a system) and conduct experiments using gears to find out how gear ratios affect the behavior of a gear system in practice.
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Elevators and Pulleys
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Your pupils can explore pulleys and pulley systems in the context of a basic elevator. Having familiarized them with the basic terms and concepts, you can supervise them in the construction of a model elevator that uses pulley systems to move up and down. Have the pupils put different loads in the elevator and adjust the pulley systems (adding or removing pulleys), noting the effects. Your pupils should observe that more pulleys make the elevator seem lighter, but that it takes longer to raise.
Inclined Planes
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The object of this lesson is to let pupils discover how a ramp makes it easier to move loads from a low place to a higher place. Have your pupils build ramps using building blocks and rulers or paint sticks. They must then adjust the angle of the ramp and, using a spring scale to measure force, make predictions and inferences about what will happen when they use the inclined plane to lift an object. Organize your pupils into pairs and have them conduct experiments, moving loads of various weights up the inclined plane and collecting data on what happens. Afterward, discuss how the data did or did not bear out their predictions.
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References
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