Students develop the concept of troubleshooting. They see how clear drawings can help in troubleshooting. Students get ideas on how to troubleshoot and fix problems from one another, then work on their own wind-ups.
See the troubleshooting ideas at the end of Lesson 2.
Select one of the issues from the chart, such as “Wind-up doesn’t go,” and ask:
If something doesn’t work the way you want it to, what should you do?
Develop the idea that it doesn’t make sense to start over, because most of what you made is probably OK. Also, if you start over, you might just run into the same issue again! It makes much more sense to:
Make a Troubleshooting chart: Write down the issue “Wind-up doesn’t go” and under it two columns labeled “Cause” and “ Fix.” Ask students what they think is causing the wind-up not to go. Record their ideas in the “Cause” column. Model one or two entries on this chart, like the one below: Then ask what they did or could do about that problem, and put the answer under “Fix.” Sometimes it’s easier to go the other way – Figure out the “Fix” first, and then decide what the “Cause” was. Model this process, by creating one entry on the chart, something like this:
Introduce “friction” as a common cause of issues:
When the issue is that the wind-up doesn’t go, a common cause is friction between a part that is supposed to move and a part that does not move, such as between the stick (which stays still) and the rest of the wind-up (which moves.) Note that friction can also be good, as the friction between a tire and the road.
Sharing issues and possible causes:
Ask students to present some of the issues that have come up with their wind-ups. Add them to the list begun in Lesson 2. After each issue is presented, ask if anyone has figured out a way to solve that particular problem.
Drawing so we can see the issue:
Sometimes, if a wind-up is clearly drawn, students can predict how it will behave. For example, If there is a lid on the top of the cup but none on the bottom (figure on bottom right, page 19), we can predict the wind-up will go in a circle when it moves. If there is nothing separating the lid from the stick, friction between the two will probably keep the wind-up from moving. Ask students to predict how the wind-ups you have drawn will behave. How should the drawings be changed to correct these problems? If there are student drawings that will illustrate the importance of accurate drawing, use these.
Students use troubleshooting ideas:
Provide time for students to get their wind-ups to work, based on one-another’s suggestions for troubleshooting