Build the car shown in the picture. Test your car by setting it on the ground. Does it move easily? If not, you may be gearing up instead of down. Try turning the worm gear capsule around.

1. Create a straight 10-foot race track for your car. Be sure to clearly mark the start and finish lines.

2. Use a stopwatch to time how long it takes your car to travel the entire 10 feet.

3. Calculate the speed of your car in feet per second and record it in your ePortfolio. Use the equation Speed = Distance / Time.

4. Repeat the test several times and record the results.

NOTE: Does your car swerve? Adjust the front and rear axles until it drives straight.

1. Using what you know about gear ratios, modify the basic car design to increase the speed of your car.

2. How fast can you make it?

3. Time your car over the 10-foot race course.

4. Calculate the speed in feet per second.

5. Record the results just like before. How does it compare to the basic car?

6. Continue to experiment with your car design—try combining different gear capsules. What happens if you rearrange the order?

7. Record the changes you made for each modification.

There are many variables that can affect your car’s performance: battery life, wear-and-tear on the parts, friction from your testing surface, etc. If your test results did not match your prediction, see if you can figure out why.