Energy systems
EnerJeeps
4. Let's Roll
Overview
In order to make an electric car, you first need to make a car. In this lesson, students create cars that will roll when given a push or released on a ramp. They confront issues of friction, and develop means for reducing it; and work on how to make their cars go straight.
Procedure
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Car talk: Before making a motorized car, students solve the problem of making a simple car that will roll easily. Ask students:
- What parts do you think you will need to make a car? Introduce the parts available for making cars.
- How will you put these parts together?
- Which parts of your car will be turning and which parts will not be? After discussing these issues briefly, provide the Worksheet for Designing a Car where students record their design ideas.
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Make a car: Provide materials for making cars, and cardboard sheets for making ramps. Students should test their cars by trying to get them to roll down ramps. It is likely that many of them will not work well. See the Troubleshooting section below. The 8 ½ x 11″ cardboard sheets may not be big enough to test the cars properly. If so, ask:
- What would make a better ramp? Where could we find a better ramp?
- Students can record the issues with the small ramp on the worksheet and hunt for a better ramp.
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Class meeting: Discuss the issues that came up and what students did to solve them. Introduce the words axle for the stick that holds the wheels, and body for the cardboard platform. There are usually two issues:
- The wheels fall off the axle
- The wheels don’t turn, or don’t turn easily. Introduce friction as a force that prevents things from moving, or from moving easily. If so, ask students:
- Where is the friction that prevents wheels from turning, or turning easily?
- How could this friction be reduced? Here are some ideas for discussing the two issues.
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Make the cars better: Provide time for students to troubleshoot their cars, and redesign them if necessary. Then use the How to Make a Car Worksheet to write a Troubleshooting Guide and a Construction Manual.
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Outcomes:
- Something that can roll will move more easily than something that can’t.
- Friction prevents something from moving easily. You have to reduce friction to allowing one part to turn while another does not.
- In order to go straight, the axles of a vehicle have to be parallel to each other.
- Word-wall words: parallel, axle, body, friction, skewer, bearing, construction manual, troubleshooting guide, issue, fix.
Assessment
Troubleshooting
There are a variety of issues that arise as students build simple cars. Each gives an opportunity to Troubleshoot. It is only by troubleshooting that students learn how to troubleshoot, so embrace these issues. These videos represent some of the issues that arise.
Wheels don’t turn easily because of one of the following:
This Troubleshooting Table organizes Issues, Possible Causes, and Fixes.