Add "Physic Material" to bullet.
var bullet_prefab : Transform; //add rigidbody, beforehand private var bullet_point : GameObject; //child of kart function Start () { bullet_point = GameObject.Find("bullet_point"); } function shot_bullet(){ //move-direction var bullet_move_direction = bullet_point.transform.position - this.transform.position; //generate var bullet = Instantiate( bullet_prefab, bullet_point.transform.position, bullet_point.transform.rotation); bullet.rigidbody.velocity = 10 * bullet_move_direction; }