2D rope attached object has no momentum when swung

Hi guys,

I'm currently trying to make a ball that is attached to a rope (made from 2d hinge joints) keep it's momentum when swung. The rope follows my mouse and when i move it around, i want the ball to have momentum so that i can swing it around like a wrecking ball or a yoyo. Currently the ball doesn't have any velocity or momentum when i swing the rope around.

This is my mouse follow code :

 private Vector3 mousePosition;
 public float moveSpeed = 0.1f;

 // Use this for initialization
 void Start () {

 }

 // Update is called once per frame
 void Update () {
     if (Input.GetMouseButton(1)) {
         mousePosition = Input.mousePosition;
         mousePosition = Camera.main.ScreenToWorldPoint(mousePosition);
         transform.position = Vector2.Lerp(transform.position, mousePosition, moveSpeed);
     }

 }

}

Thanks for any help!