Trying to stop a RigidBody that is moving

Unity Engine
1

i gave a rigidbody a velocity at void start(), and i want it to stop once it reaches a certain point in the screen.
tryed doing rb.velocity = Vector3.zero and such, but couldnt find any thing thet worked even after searching the forum.

void Start()
    {
        changedSpeed = false;
        rb = GetComponent<Rigidbody> ();
        if (this.tag == "Boss") {
            rb.velocity = transform.forward * speed;
            ///////
        } else {
            rb.velocity = transform.forward * speed;
        }
    }

    void FixedUpdate ()
    {
        if (this.tag == "Boss") {
            rb = GetComponent<Rigidbody> ();
            if ((rb.position.z <= 13.5) && (changedSpeed == false)) {
                string messege = string.Format("position z = {0}, speed = {1}", rb.position.z, rb.velocity.ToString());
                Debug.Log (messege);
                rb.velocity = Vector3.zero;
                rb.angularVelocity = Vector3.zero;
                rb.angularDrag = 0;
                messege = string.Format("position z = {0}, speed = {1}", rb.position.z, rb.velocity.ToString());
                Debug.Log (messege);
                changedSpeed = true;
            }
        }
    }
2

Well your object should stop when you set velocity to zero. Are you adding force anywhere else? Do you have any friction? Are your Debug.Log called?

As a last resort you could set rb.isKinematic to true. When you want you object to move again, you will need to set it back to false

3

ohh shit, i saved the starting speed in another script and inputed velocity there… thanks!