Downhill Racer

A primary goal of this lab is for students to practice controlling variables. Many things can affect the distance the cars roll: type of car, height of the ramp, exact location of the ramp in the room (since some parts of the floor may be bumpier than other parts), position of the starting line on the ramp, how the car is released, and “accidents” (e.g., bumping the side of the ramp). Of all these variables, only the ramp height is allowed to change; the others must stay fixed.

For this reason and to help students stay focused during the lab, they should be familiar with the equipment before they begin. The following steps can help:

1. Students bring in cars from home several days before the activity.
2. Set up a ramp area (or two) with inclines, blocks or books, and metersticks. See Figure 1.
3. Let the children play with the cars informally during free time for a few days. You might suggest a “roll-off” during recess.
4. Ask students to identify “good rollers.” A good roller will roll straight for about 2 meters or more.
5. Discuss “What variables affect how far a car rolls?” (floor surface, type of car, ramp incline, starting line, release of car)

Be sure students have completed DPP items O and Q. These items will prepare students for scaling their graph in the lab by practicing skip counting by 0.1s, 0.01s, 0.25s.