title: Unity 3d player jump does't work, rb.addforce doesn't work
body: <p>I have a very basic <code>infinite runner</code> and I want to make my player jump. I have attached <code>rigidbody</code> to my player, have instantiated it. here is some part of my code</p>
  
  <pre><code> void FixedUpdate()
  {
      if (OnGround)
      {
          if (Input.GetKeyDown(KeyCode.Space))
          { 
              rBody.AddForce(new Vector3(0, 10, 0), ForceMode.Impulse);
              Debug.Log("jump");
              OnGround = false;
          }
      } 
  }     
  
  void onCollisionEnter(Collision other)
  {
      Debug.Log("collision");
      if (other.gameObject.CompareTag("ground"))
      {
          OnGround = true;
      }
  }
  </code></pre>
  
  <p>I have tried to put this part in <code>Update()</code>, no result.
  The interesting part is that <code>Debug.Log("jump")</code> shows on the console, but the player doesn't want to jump.
  Method <code>void CollisonOther()</code> is never called.
  I have also tried to change <code>velocity</code> and use <code>transform.translate</code>, no result</p>
  
  <p>jump. How can I make it jump?</p>