How to smooth/damp a movement?

Can you tell a newbie how to smooth/damp this script? What i'm trying to achieve is when i tap the screen to reverse gravity immediately and when i tap again vice versa but instead it takes couple of seconds to do it .Can you help me?

 public GameObject playerObject=null;
 public float moveSpeed;
 Rigidbody2D player;




 void Start () {
     player = playerObject.GetComponent<Rigidbody2D> ();

 }
 

 void FixedUpdate () {

     player.velocity = new Vector2 (moveSpeed,player.velocity.y);

     for (int i = 0; i < Input.touchCount; i++)
     {
         Touch touch = Input.GetTouch (i);

         if (touch.phase == TouchPhase.Ended && touch.tapCount == 1 ) 
         {
             Vector3 position = Camera.main.ScreenToWorldPoint (touch.position);

             if(player.gravityScale==0.5f)
                 player.gravityScale=-0.5f;


             else
                 player.gravityScale=0.5f;

         }


         }


         }
 

}