How to enable gravity with the following script(HELP)

@Hellium
Hi guys i have the following script
public enum Direction
{
North,
South,
East,
West
}

public class Cuboid : MonoBehaviour
{

public float rotationSpeed = 250;

private bool _moving;
private Direction _rotationDirection;
private Vector3 _pivot;
private float _totalRotation;
private Vector3 _axis;
private Vector3 _scale;

void Start()
{
    _moving = false;
    _scale = transform.localScale / 2.0f;
    rigidbody.GetComponent<Rigidbody>();
}

void Update()
{

    if (_moving)
    {
        float deltaRotation = rotationSpeed * Time.deltaTime;
        if (_totalRotation + deltaRotation >= 90)
        {
            deltaRotation = 90 - _totalRotation;
            _moving = false;
        }
        if ((_rotationDirection == Direction.West) || (_rotationDirection == Direction.North))
            transform.RotateAround(_pivot, _axis, deltaRotation);
        else transform.RotateAround(_pivot, _axis, -deltaRotation);

        _totalRotation += deltaRotation;
    }
    else if (Input.GetKeyUp(KeyCode.W)) Rotate(Direction.North);
    else if (Input.GetKeyUp(KeyCode.A)) Rotate(Direction.West);
    else if (Input.GetKeyUp(KeyCode.S)) Rotate(Direction.South);
    else if (Input.GetKeyUp(KeyCode.D)) Rotate(Direction.East);

}

void Rotate(Direction direction)
{
    _rotationDirection = direction;
    _moving = true;
    _totalRotation = 0;

    switch (_rotationDirection)
    {
        case Direction.East:
            _pivot = transform.position + new Vector3(_scale.x, -_scale.y, 0);
            break;
        case Direction.West:
            _pivot = transform.position + new Vector3(-_scale.x, -_scale.y, 0);
            break;
        case Direction.North:
            _pivot = transform.position + new Vector3(0, -_scale.y, _scale.z);
            break;
        case Direction.South:
            _pivot = transform.position + new Vector3(0, -_scale.y, -_scale.z);
            break;
    }

    if ((_rotationDirection == Direction.East) || (_rotationDirection == Direction.West))
    {
        _axis = Vector3.forward;
        float temp = _scale.x;
        _scale.x = _scale.y;
        _scale.y = temp;
    }
    else
    {
        _axis = Vector3.right;
        float temp = _scale.z;
        _scale.z = _scale.y;
        _scale.y = temp;
    }
}

}
I want the cuboid to fall of through a hole.So i enabled gravity but then gravity affects the cuboid script
Please Help
Any help would be appreciated
Thanks A LOT!!!

Solution in this case. Change your Start function to this.

 void Start()
 {
     _moving = false;
     _scale = transform.localScale / 2.0f;
     rigidbody.GetComponent<Rigidbody>(); // What exactly you are doing here. Remove this line.

     rigidbody.GetComponent<Rigidbody>().useGravity = false;  // this rigidbody will not use gravity

 }

P.S
Whenever you want cuboid to fall off use.
rigidbody.GetComponent().useGravity = true;

Thanks i will try this out