I've been reading a book call "Robert Penner's Programming Macromedia Flash MX" and just typed/modified his Vector Class that he uses to do velocity and Acceleration. Interesting stuff. If anyone wants the code that I modified for KM let me know.

Snippet :
Code:
//Math Functions needed in Vector class

atan2D=function(y,x){

   return Math.atan2(y,x)*(180/Math.PI);

   }

cos2D=function(angle){

   return Math.cos(angle*(Math.PI/180));

   }

sin2D=function(angle){

	return Math.sin(angle*(Math.PI/180));

	}

acosD=function(ratio){

	return Math.acos(ratio)*(180/Math.PI);

	}

	

//Vector Class	

function Vector(x,y){

   this.x=x;

   this.y=y;

   };

Vector.prototype.toString=function(){

   var rx=Math.round(this.x*1000)/1000;

   var ry=Math.round(this.y*1000)/1000;

   return "["+rx+","+ry+"]";

   };

   

Vector.prototype.reset=function(x,y){

   this.constructor(x,y);

   };