Friction equations?

I have a billiard ball system, whic detects collisions between balls and modifies their x and y velocities accordingly.

I have included a friction variable and I have a very basic system for applying the force of friction for each iteration of movement:

private static var FRICTION:Number = 0.94;

public function move() : Void
mc._x += vx;
mc._y += vy;




This works to a reasonable level of satisfaction, but it doesn’t quite feel right. The balls seem to take just a little too long to stop when they’ve slowed down to a very small velocity. I’ve tried tweaking the friction constasnt, but I still can’t get sometthing that feels exactly right.

Can anyone enlighten me on a more effective method to account for friction when moving balls across a given surface?