I have a planetary gravity script; how do I make the object speed up?

Basically, I have a planetary gravity script and it works okay. It pulls any objects with a rigidbody towards it, but it moves towards it at the same speed. What do I add to the script to make the object speed up as it falls?

var range : float = 30.0;
function FixedUpdate () {
	var cols : Collider[] = Physics.OverlapSphere(transform.position, range);
	var rbs : Array = new Array();
	for (c=0;c<cols.length;c++) {
		if (cols
.attachedRigidbody && cols[c].attachedRigidbody != rigidbody) {
    			var breaking :boolean = false;
    			for (r=0;r<rbs.length;r++) {
    				if (cols[c].attachedRigidbody == rbs[r]) {
    			if (breaking) continue;
    			var offset : Vector3 = (transform.position - cols[c].transform.position);
    			var mag: float = offset.magnitude;
    			cols[c].attachedRigidbody.AddForce(offset/mag/mag * rigidbody.mass);

Perhaps some expression of time in AddForce? Or maybe just some moveFaster += 1; for some linear action in your life. Perhaps play with ForceMode