Error in script

Questions & Answers
1

I understand this is really simple, but for some reason I can't get the thing to start after 20 seconds.

function FixedUpdate () {
    Invoke(rigidbody.AddForce, 20);
    rigidbody.AddForce (Vector3.up * 3000);
}

It basically turns on the addforce function after 20 seconds.

3

First, I'm not an expert on Invoke, but when I looked it up the manual, it takes a string argument. Second, do you really want to call it in FixedUpdate, which runs (roughly) every frame? If I read that last line correctly, you wanted it to start after 20 seconds.

var startForce = true;

function FixedUpdate() {
    Invoke("UseTheForce", 20);
}

function UseTheForce() {
    if (startForce) {
         rigidbody.AddForce (Vector3.up * 3000);
         startForce = false;
    }
}

This would run one time. Again, I'm not sure of your intent - if you wanted it to repeat, then get rid of the boolean. Better yet, use InvokeRepeating and call it from the Start() function.

2

You need to reference the object that the AddForce is being applied to, through a gameObject or gameObject.Find("object name").