## Overview

Students discuss different ways to make wind-ups. The term “variable” is introduced as a way to think of differences among wind-ups. Students decide on a common way to make a wind-up, then make a second wind-up following the agreed plan.

Wind-ups that differ in parts and construction, those prepared by the teacher as well as those made by students in Lesson 2. These are wind-ups with two paper plates as wheels, one lid for a wheel, or two lids as wheels, different sticks, or different cups or tubes to separate the wheels.

## Materials

• Materials for making the second wind-up, the same for each student : skewers, cups, one size of rubber bands, cup lids, masking tape, paper clips, pony bead, push pins or other object for making holes.
• Note: The best rubber bands are 1/8" wide and the length of the paper cup. We use a #33 or two # 30 linked together for an 8 oz. cup.

## Procedure

1.      Class meeting: Differences among wind-ups: Display three or four wind-ups having different designs. Students discuss ways in which wind-ups can differ.  List the ways students suggest. Include wheel size, stick size, and how the two wheels are separated.  If no one has mentioned rubber bands and amount of winding as other ways wind-ups differ, show a variety of rubber bands.

2.      Introduce “variables”: Each of the ways we can change a wind-up, such as wheel size, type of rubber band, or amount we wind it up, is what scientists call a “variable”. Each time we change a variable, we might change the way the wind-up works.

3.      Prepare for wind-up experiments: make identical wind-ups: Introduce the idea that students will experiment with their wind-ups. First they must each have the same kind of wind-up.  Help students decide on how to make a common type of wind-up, keeping wheels, rubber bands, sticks, beads, and cups the same.  In Lesson 6 students make wind-ups with large (paper plate) wheels to compare to those with smaller wheels, so now they should use cup lids.

4.      Make a new wind-up: Discuss the design of the new wind-up and list the parts to be used.  Then each student makes a second wind-up according to the agreed design. Each student must make a note of anything that did not work in this new wind-up, and how they fixed it. These notes will be used to write a Troubleshooting Guide in Lesson 5.

5.      Draw and label your wind-up. Distribute the worksheet "Draw and Label your 2nd Wind-up".  Students complete this drawing, which will be used in Lesson 5.

6.      Outcomes

7.      Word wall words:  variable.