Centrifugal Force

Question: Does Centrifugal force really exist?  If not, then why do so many 
people use it to explain everyday occurrences?  For example, when you swing a 
bucket of water around, what keeps the water in?  Most people would say 
centrifugal force.
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Yes, this idea does have a sound meaning and valid existence.  It 
does not represent a "real" force in the sense that Newton uses, which is:  
something that gives rise to accelerations in a reference frame which is not 
rotating or being accelerated (a frame in which objects at rest tend to stay 
at rest unless acted on by a force) (these frames are called inertial frames).  
However, in a rotating reference frame (or coordinate system) such as a merry 
go round, objects that are at rest tend to slide and objects with no "real" 
force do not move in straight lines.  Have you ever tipped over a glass full 
of liquid in a turning car?  From the point of view of the rotating coordinate 
system what tipped the glass over is the "centrifugal force".  From the point 
of view of the inertial frame of reference outside the car, the glass was 
still trying to go forward in a straight line when the car turned and the 
force acting on the bottom of the cup flipped it over.  Both perspectives are 
valid and you can calculate the results from both perspectives as dictated by 
convenience, but there is no "real" force of this type.  It is however very 
useful to think this way.

Sam Bowen
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