Let's say I have a pen up in space in a zero g environment. And I carefully give the pen a nudge at the very tip of it. That's pretty away from the center of the mass of the pen. I know that will exert a torque and the pen will spin but I want to know whether its center of mass (along with the whole body) will move in a forward direction or not? And If yes how am I going to calculate how much it will move forward?