well, it will travel 4 meters if you build it correctly, as in VERY PERCISE!
Also, you can try this:
You build a basic car, with a
body and a way to support the front wheels and the back wheels. Each set
of wheels should be firmly attached to an axle, maybe a piece of dowel, so
that when the axle turns, so do the wheels. Then you need some way to
attach the end of a strong rubber band to the middle of each axle so that
when you rotate the wheels, the rubber band winds around the axle and
stretches tight. You can do this with a small nail or screw put carefully
through the dowel. The best way to wind the wheels is probably to push down
on the car while you push the car along a surface, like carpet. My
two-year-old son has a toy car that winds up this way (but it uses a spring
instead of a rubber band). Anyway, once the rubber band is really tight,
you let the car go, and the stored energy in the rubber band unwinds the
axle, and off goes the car. You don't have to have the band wind around
both axles ... you could make it either just front-wheel drive or
rear-wheel drive, but it probably goes better if you use both axles. You
could also use two rubber bands, one for the front wheels and one for the
back wheels, with the ends of each rubber band fixed to the middle of the
car. Remember, the car will go fastest and the most distance if you use a
really BIG strong rubber band, and can wind it up around the axles really
really tight. But if you make it TOO tight or too strong, the car or the
axles might break when you wind it up, which is not good and really annoying.
Another way of making a car like this is to make it like the rubber-band
powered toy airplanes. Make a light frame with 4 wheels, and buy a little
toy propeller or take it off a toy airplane, then wind up the rubber band
by winding the propeller. Then when you let go the propeller, it will drive
the car along.
http://www.serve.com/chunter/index/info/cars.html
