Hitting a ball straight

Getting Started
1

Hey guys I hope someone can help this has been doing my head in for hours! I am trying to hit the cue ball straight regardless of whether you hit the cue ball on the far right, far left or centre, they should all send the white in a straight line as if I hit the cue ball in the middle of the white. I am adding my own force like this:

Vector3 forceDirection = cueTip.transform.up;
forceDirection.y = 0;
rb.AddForce(forceDirection*1000, ForceMode.Impulse);

I drew a line from the cue ball in the direction of CueTip.up and this is the correct line, however when I hit the ball the force does not send the white straight like I want, can anyone see why?

Here is an example:

https://postimg.org/image/gx1nrqeh9/

The left image is what is happening, but I want the the right image effect, from what I can see above I have no idea why the left is happening because the cue would be pointing straight forward not to the left.

2

Did you try to use the vector3.forward or transform.forward vectors when applying the force?

3

Do you have regular collisions in between the ball and the cue? That could mess things up.

In this case I would consider using setting Velocity directly instead of AddForce.