find the relative velocity of a rigidbody in unity code example

Example 1: unity how to set rigidbody velocity

Vector3 velocity = new Vector3(10f/*x*/, 10f/*y*/, 10f/*z*/);
GetComponent<Rigidbody>().velocity = velocity;

Example 2: rigidbody.velocity.magnitude

//speed of rigidbody in m/s
float speed = rigidbody.velocity.magnitude;