Movement in a frictionless environment

Hi, could anyone tell me where to find some info about generating movement on a frictionless environment? I need to put a ball running in a window, given an initial speed and then let it run along with the rules of phisics....can anyone give me a hint on where to find info, or on how to do that? I would be most greatefull. Thankx ----->R.Daniel ICQ 28959546