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The information below is intended to provide introductory material
for elementary students and further material for high school students.
Please keep in mind that not all demonstrations are presented
at each show, and each topic may not be covered.
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An object traveling in a circle behaves as if it is experiencing
an outward force. This force, known as the centrifugal force,
depends on the mass of the object, the speed of rotation, and
the distance from the center. The more massive the object, the
greater the force; the greater the speed of the object, the greater
the force; and the greater the distance from the center, the greater
the force.
It is important to note that the centrifugal force does not actually
exist. We feel it, because we are in a non-inertial coordinate
system. Nevertheless, it appears quite real to the object being
rotated. This is because the object believes that it is in a non-accelerating
situation, when in fact it is not. For instance, a child on a
merry-go-round is not experiencing any real force outward, but
he/she must exert a force to keep from flying off the merry-go-round.
Because the centrifugal force appears so real, it is often very
useful to use as if it were real. The more massive the object,
the greater the force. We know that this is true because an adult
will have a harder time staying on a merry-go-round than a child
will. The greater the speed of rotation, the greater the outward
force. We know that this is true because a merry-go-round is harder
to stay on, the faster it rotates. If you move further out on
the merry-go-round, you will have to exert a greater force to
stay on. In order to stay on a circular path, we must exert a
force towards the center called centripetal (or "center-seeking")
force. Consider a rope with a ball on the end. You can swirl the
ball around in a circle over your head while holding onto the
rope. The ball experiences the so-called centrifugal force, and
it is the rope that provides the force to keep in moving in the
circle.
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Fc = mv2/r, where Fc = centrifugal force, m = mass, v = speed, and r = radius.
An object traveling in a circle behaves as if it is experiencing
an outward force. This force is known as the centrifugal force.
It is important to note that the centrifugal force does not actually
exist. Nevertheless, it appears quite real to the object being
rotated. For instance, a child on a merry-go-round is not experiencing
any real force outward, but he/she must exert a force to keep
from flying off the merry-go-round. The child believes that he/she
is in an inertial frame of reference, when in fact he/she is not.
An object traveling in a circular motion is constantly accelerating
and is therefore never in an inertial frame of reference. Since
the centrifugal force appears so real, it is often very useful
to use as if it were real. The equation above shows that the force
depends on v-squared over r. Because v increases with radius,
the force will actually increase with radius as well. If you are
standing on the merry-go-round, you will have a harder time staying
on as you move further away from the center if the merry-go-round
rotates at a constant speed.
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The following demonstrations illustrate this physics topic:
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Sponsored by the Physics Department and the Center for Science, Mathematics, and Engineering Education -- University of Virginia
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