mouse trap car?

hey i was wondering if any1 has some ideas bout how ta make a mouse trap car thet has good speed and distance and able ta stop at 4 feet? i plan to use gears but idk how ta get it to stop...

I suggest using a C STr engine with some Balance springs. Use shallowish wood.

uhm.. i dont think we're allowed ta use engines.. ^.^; just simple machienes... like levers, pullys, gears, screws...