Unity script to shoot a ball

ShootBall.cs

using UnityEngine;
using System.Collections;

public class ShootBall : MonoBehaviour {

  float timer = 0.0f;
  float timeLimit = 1.0f;
  bool  shootSwitch;

  // Use this for initialization
  void Start () {
    shootSwitch = true;
  }
  
  // Update is called once per frame
  void Update () {
      timer += Time.deltaTime;

      if((timer > timeLimit) & shootSwitch) {
        float z = 2000; // force strength;
        Rigidbody rigidbody = GetComponent<Rigidbody>();
        rigidbody.AddForce(0, 0, -z);

        timer = 0.0f;
        shootSwitch = false;
      }

  }

}

its asking for shoot switch but I cant find that on his acc