hey every1.. at the moment for a school project a group of mates and i are building a rat trap operated car. This is made by obviously a rat trap with about 5mm diamater front wheels and cds as the rear wheels... this is just a quick explanation. what i need to do is find out how far the car will go and what speed it will be. i thought that the distance = circumfrence of the back wheels * revolutions of the axle (has the string tied to t). however im pretty sure this is just finding out the distance the car will travel from start to when the string is fully unwound (not past that). so now im abit confused and trying to find out a way to find out the distance covered from the momentum. but not sure so if anyone has any suggestions it would be appreciated. cheers note - info on rat/mouse trap operated cars can be found from a google search.