I get a little bored of reading these threads that are so long they end up going around in circles. As a result I havent read all the replies, so I apologise if I am repeating what someone else has already said.. .. .I am going on what I was taught in O level physics. I am not a professor in Newtonian physics, but I am a trained engineer.. .. .As far as I can make out this force is usually termed cenripetal by physics teachers and engineering lecturers. Everyone else uses centrifugal. Whatever you use, it is a reaction force. . .. .As a blade, wheel or your underwear spins round, its velocity constantly changes, (velocity being defined as rate of change of distance with time in a straight line). If velocity is constantly changing, then there must be acceleration (acceleration being rate of change of velocity with time). Now Newton steps in with his third law, stating that a body that has mass and is being accelerated, must have a force associated with it. That force being centri******.. .. .Nothing to do with inertia, momentum etc, just the simple fundamentals of mechanics. Dont use intuition to understand, use basic facts.