this one was for a physics class, but i've had to make them for introductory engineering classes as well. the string goes from the lever to the pulley, and from the pulley it winds around the rear axle. you wind the rear wheels up, wrapping the string around them, which pulls the lever up and sets the car. once you let go, the lever spins the axle.
man, lotsa hate for givin ubuntu some advertising.
they were supposed to go 4 m. this one made it 3.3. some questions we had to answer along with my actual answers:
Did your car make it 4 m?
No, 3.3, but it looked good doing it!
What materials were used on your car and why did you use them?
(skipping the boring stuff)
Chrome Duck Tape - bling
BMW Roundel - weight, awesome
What advice would you give to future students?
Test your car on the same surface on which it will be graded. Also, use lots of chrome duck tape and BMW roundels!