hi I know that this script is seen often but I have an another problem with a damage and health scripts. I think it's the GetComponent part, well anyway if you could help that would be great.

/PlayerHealth/

 using UnityEngine;
 using System.Collections;
 
 public class PlayerHealth : MonoBehaviour {
     public int maxHealth = 100;
     public int curHealth = 100;
     
     public float healthBarLength;
 
 
     void Start () {
     healthBarLength = Screen.width / 2;
     }
     
 
     void Update () {
     AddjustCurrentHealth(0);
         
     }
     
     
     void OnGUI(){
     GUI.Box(new Rect(10, 10, healthBarLength, 20), curHealth + "/" + maxHealth);    
     }
     
    
     public void AddjustCurrentHealth(int damage) {
       curHealth -= damage;    
         
         if(curHealth < 0)
             curHealth = 0;
         
         if(curHealth > maxHealth)
             curHealth = maxHealth;
         
         if(maxHealth < 1)
             maxHealth = 1;
         if(curHealth == 0)
         {
             Destroy(gameObject);
         }
         healthBarLength = (Screen.width / 2) * (curHealth / (float)maxHealth);
     }
 }

/bullet/

using UnityEngine; using System.Collections;

public class bullet : MonoBehaviour { public int Damage = 10; public float Speed = 1500f; public float lifetime = 5f;

 void Start()
 {
             
     rigidbody.AddRelativeForce(new Vector3(0,0,Speed), ForceMode.Impulse);
     Destroy(gameObject, lifetime);
 }
 void Update()
 {
     
 }
 void OnTriggerEnter (Collider col)
 {  
     print("y1");
     if(col.tag == "Player")
     {
     col.gameObject.SendMessageUpwards("AddjustCurrentHealth", Damage, SendMessageOptions.DontRequireReceiver);
     print("y2");
     }    
 } 

}