How do I apply a force to the other object in a collision?

I'm really new at this. Right now I have a sphere that is bouncing around in a flat level.

I've used materials to keep the sphere from losing energy if it hits the floor, but now I would like to add a section of floor that if the sphere lands on top of, will add force to the sphere in the upwards direction.

Is there a script I could add to the specific section of floor that basically says "if an object collides with me, add force to that object in the upwards direction."

More info:

-The section of floor is currently a box collider.

-The sphere is a sphere collider and a rigidbody.

After a bit of googling I came across something like this (I messed around with the 1700 to just try to see if it wasn't enough force):

function OnCollisionEnter(collision : Collision) {
    if (collision.rigidbody) {
        collision.rigidbody.AddForce (Vector3.up * 1700);
    }
}

but it doesn't work when I put the code on the floor section. Would you be able to explain how to do what I want and why the above code doesn't work?

Thanks.