Can someone help me fix this coding error?

Before I show the code, I would like to explain I did try to fix it and my fix worked kind of, but caused other errors to show up and I just didn't feel like typing all of the errors out on here and I already know it wasn't the right kind of fix I needed. Anyways, here is the code I used

 #pragma strict
  
  var rotationSpeed = 100;
  var jumpHeight = 8;
 
  private var isFalling = false;
 
  function Update () 
  {
      //Ball rotation.
      var rotation : float = Input.GetAxis ("Horizontal") * rotationSpeed;
      rotation *= Time.deltaTime;
      var rigidbody: Rigidbody = gameObject.GetComponent(Rigidbody) as Rigidbody;
     GetComponent.<Rigidbody> ().AddRelativeTorque (Vector3.back * rotation);
 
     if (Input.GetKeyDown(KeyCode.Space));
 
     {
         Rigidbody.velocity.y = jumpHeight;
     }
     isFalling = true;
  }

And the error that showed up is "An instance of type 'UnityEngine.Rigidbody' is required to access non static member 'velocity'"