In this clip you can see that I have used a deferent amount of frames for each animated car, to achieve the illusion in the difference in speed at which they cross the screen.
I downloaded the images of the red car above from google images, and uploaded it into Flash. I then used the brush tool to draw over the image my own car. I then deleted the original image of the car, leaving my outline drawing underneath which I used for my animation.
I created the different speeds in the two cars by selecting that I want each car to move from one end of the screen to the other, then choosing how many frames I want this movement to take. In this case I chose the car in layer 7 to have twice as much frames as the car in layer "car", which in hand created twice as many frames. This meant that the car in layer "car" would complete the set distance in twice as little frames as the car in layer 7, therefore creating the illusion that it moves faster.
I used the tool motion tween to make Flash auto-create the frames between the selected movement.
Creating this animation thought me 2 new techniques. One was that I can draw over another image to create a drawing, this allowed me to draw my car much faster and and much more accurately than if I hadn't used the image. The second technique was that By creating less frames for the movement of an object, I can make it move faster than it would with the normal speed.