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