how i know my object speed ?

hi ,
please how i can know the speed of my object i shooted it .
because i want to execute function when this object stop and it speed = 0 .
I,m still new in unity :frowning:
function Shoot(){

var ball= Instantiate(Ball, transform.Find("me").transform.position, Quaternion.identity);
ball.rigidbody.AddRelativeForce(transform.forward * Force );