Why object goes sometimes through walls by adding force ?

I want to throw a grenade (with Rigidbody and Collider). Therefore I use AddForce () and it is working. However if I throw the grenade, it sometimes goes through walls, even though the walls and the grenade have colliders. Please help me.

This is my code:

  using UnityEngine;
  using System.Collections;
  
  public class ThrowGrenade :MonoBehaviour
  {
      public GameObject grenadePrefab;
      public Transform grenadeSpawnPoint;
      public float throwForce = 20f;
      public float delay = 2f;
  
      void Update ()
      {
          if (Input.GetKeyDown (KeyCode.F))
          {
              GameObject go = Instantiate (grenadePrefab, grenadeSpawnPoint.position, grenadeSpawnPoint.rotation);
              go.GetComponent<Rigidbody>().AddForce (grenadeSpawnPoint.forward * throwForce, ForceMode.Impulse);
              Invoke ("Explode", delay);
          }
      }
  
      void Explode ()
      {
          //Explode
      }
  }

And sorry fro my bad English, because it isn't my native language.