There is an error with he rotationSpeed and I can't fix it

#pragma strict

function Update () 
{
    var rotation : float = Input.GetAxis ("Horizontal") * rotation Speed;
    rotation *= Time.deltaTime;
    rigidbody.AddRelativeTorque (Vector3.back * rotation);
}

If this is the actual code you’re trying to use then I don’t see how it would compile. I don’t see where you’ve defined rotationSpeed, and on line 5 you have a space in your variable name (if it is that). ‘rotation Speed’ should probably read ‘rotationSpeed’, and it needs to be defined somewhere if it isn’t already.

Also, any physics stuff you do should be in the FixedUpadte function, so all in all your code should look like this:

var rotationSpeed : float = 5;

private var currentRotation : float;

function Update () 
{
    currentRotation = Input.GetAxis ("Horizontal");
}

function FixedUpdate()
{
    rigidbody.AddRelativeTorque (Vector3.back * currentRotation * rotationSpeed * Time.fixedDeltaTime);
}

I haven’t tested it, but it is theoretically correct.