Pick 2D object with touch in Unity 4.3

Hi, I want to pick an object (2D) with touch and move object swipe this with finger in Unity 4.3. Currently I am moving object with swipe on whole screen but I want to move object with swipe on desired object. I am doing moving object with swipe. if(Input.touchCount>0 && Input.GetTouch(0).phase == TouchPhase.Moved) {

         Vector2 touchdeltaposition = Input.GetTouch(0).deltaPosition;
         anglex = (float) (touchdeltaposition.x * Time.deltaTime *10.0);
         angley = (float) (touchdeltaposition.y * Time.deltaTime *10.0);
         elevationAngle = new Vector3(anglex,angley,0); 
         Vector3 elevation = Quaternion.Euler(elevationAngle)*transform.forward;
         rigidbody2D.AddForce(elevation);
         //if(anglex>0)
         rigidbody2D.velocity= new Vector2(anglex,angley);
     }