How to Make a (Theoretically) Perfect Mousetrap Car

Hello and welcome to my instructable.
This instructable explains how to use Math to figure out how to make a mousetrap vehicle move from a starting position and stop directly on a finishing line.*
*Disclaimer: This is THEORETICAL. Whether it will work or not is to the discretion of the build quality, but it will work if you build the vehicle well.

Pencil
Paper
Calculator
String
Permanent Marker
Axle of car

For this step, you must find the Circumference of one of your wheels.
First, take one of your wheels (or draw one with a compass if you are following along on paper) and measure from one edge to the other. Take the measurement you get and write it down so you do not forget it.
Next, take your diameter and multiply it by pi (3.141592....)
That will give you the diameter. You may want to round your number to the nearest hundredth depending on how long your decimal is.

Next, we must find the amount of rotations, but before we can do that, we must find the distance between the starting point and finish line. This can either be given to you by the lab/event coordinator or you must measure it. Next, divide the distance by your circumference (MAKE SURE THEY ARE IN THE SAME UNITS) and you will get your rotations.

In order for the mousetrap vehicle to work, you must have string that is attached to the mousetrap and the front axle. Take your string and wrap it around the axle the number of rotations we got in the last step. When you reach the number of rotations, mark the excess string with a permanent marker and trim the excess off.

Now that you have found how long your string must be, you can test you vehicle with confidence that it will work. Now, to summarize
1. Find Circumference of your wheel.
2. Find/Get distance that vehicle must travel.
3. Divide distance by circumference to find rotations.
4. Wind string on axle the amount of rotations you found.
5. Cut off excess string.
6. Celebrate
7. Vote for me in the Make it with Math contest ;)