first off, thanks for all the help. My physics book got taken when my car got broken into and my backpack was taken. I have an old book and my pages dont coencide with my homework. everyone has been a big help. with that,, i just have two final questions about centripetal force: 1. A ventilation fan has blades 0.25 m long rotating at 2 rad/s. What is the centripetal acceleration of a point on the outer tip of a blade? 2. An airplane is a wide sweeping "outside" loop can create zero "g" (weightlessness) inside the aircraft cabin. What must be the radius of curvature of the flight path for an aircraft moving at 70 m/s to create a condition of "weightlessness" inside the aircraft? Im really not sure where to start with these, although I do realize that I need to account for gravity, just not sure what kind of equation im looking for.