[quote user="Otto"]
Sigh... Centrifugal force is just as real as centripetal force is. It all depends on your frame of reference (or if you prefer, "coordinate system"). A rotating frame of reference is every bit as valid as an inertial one, if you're inside it.
[/quote]
Newton's Laws are only valid in an inertial frame. A rotating frame of reference is therefore not "every bit as valid" as an inertial one.
A good example is a frame which is falling to Earth with acceleration 2g. From this frame it appears that an "anti-gravity" force exists which causes anything not tied down to move upwards with acceleration g. Is that force "real"? Do we really have to accept "anti-gravity" as fact in order to analyze what happens? No. We simply accept it as a pseudo-force - an artefact of using a non-inertial frame.
But, if we wanted to calculate in this 2g frame a lot, we might just use this "anti-gravity" pseudo-force to make our calculations a bit easier. Would "anti-gravity" be any more real then?
It's the same for rotating frames and centrifugal force.
[quote user="EddiePedant"]
But I don't know why people get so precious about forces and pseudo-forces.
[/quote]
Actually I take that back.