Having trouble getting triggers to work with two moving cubes

Questions & Answers
1

The script I have here is attached to the falling cube, and is using a Sphere collider with trigger unmarked. It is attached to a prefab that is instantiated above the screen and dropped into the scene. The idea is that once it reaches it's intended Y value it will enable the boolean "canKill" and will destroy any trigger items it is touching. I have not been able to get the triggers to recognize an OnTriggerEnter or OnTriggerStay. What am I doing wrong?

Below is the script attached to the falling cube.

private var yVal : int;
var speedToDrop : float = 10;
static var canKill : boolean = false;
private var inBlastRadius : boolean = false;

function Awake ()
{
    yVal = crossHair.dynamiteY;
}

function Update () 
{
    var thisVector3 : Vector3 = this.transform.position;
    if(thisVector3.y <=  yVal)
    {
        canKill = true;
        Destroy(this.gameObject);
    }

    this.transform.Translate(0, 0, speedToDrop * Time.deltaTime);
}

function OnTriggerEnter(hit : Collider)
{
    Debug.Log("Entered");
    inBlastRadius = true;
    if(canKill && inBlastRadius)
    {
        Destroy(gameObject);
    }
}

function OnTriggerExit(hit : Collider)
{
    inBlastRadius = false;
}

function OnTriggerStay(hit : Collider)
{
    Debug.Log("In trigger");
    inBlastRadius = true;
    if(canKill && inBlastRadius)
    {
        Destroy(gameObject);
    }
}

The other cube is moving horizontally across the screen with a sphere collider marked Trigger.

2

http://unity3d.com/support/documentation/Manual/Physics.html

You didn't mention if the Prefab had a rigidbody or trigger attached. But the above link has a table towards the bottom that shows with what other objects a trigger will actually go off.