Converting forces from world to local frame

I am sure this has been asked many times, but I cannot find it, or get my head around it.

I have an object O whose rotation within the world frame is represented by Quaternion OW. It has forces on it within the world frame represented by a Vector3 FW.

I need to convert those forces to another Vector3 FL within O’s local frame of reference.

Am I right in thinking

FL = Quaternion.Inverse(OW) * FW

If not, what should it be? If so, why?

Yes

FL = Quaternion.Inverse(OW) * FW

should do what you want. Since a force is just a direction, just rotating it is enough.

Thanks. Looking for a good description of Quaternions.