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.
Replies:
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.
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