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Re: Periodic motion vs. oscillation



Hi,
In my mind "periodic motion" is a fairly general
term for motion the repeats itself after a set
length of time. I am working from memory of a
discussion from 15 years ago, so I may get this
next part wrong. Periodic motion has (at least )
two major subclasses: Oscillations and Rotations.
Functionally, rotations are described by an ever
increasing variable, for example an angle that
describes the position in an orbit. This variable
is often expressed modulo something, continuing
the example the orbit angle is always between 0
and 2 Pi.

Variables describing oscillations do not wrap
around, for example the angle associated with a
pendulum is limited to a range ( -theta_max to
theta_max).

I recall that there where subtle mathematical and
physical differences between the two, but I do not
recall what these are. I do remember an
interesting bit: For orbits dscribed in spherical
coordinations theta (longitude) is assocated with
a rotation while and phi (latitude) is associated
with an oscillation.

Thanks
Roger




Robert Cohen wrote:

What, if any, is the difference between periodic motion and
oscillations?

For example, the motion of the earth around the sun is an example of
periodic motion. But is it an example of an oscillation?

I thought that an oscillation is when something is forced back to some
equilibrium position (like a vibration). Periodic motion, on the other
hand, is something that repeats itself (i.e., is cyclic). Perhaps an
oscillation is an example of periodic motion but not all periodic
motions are oscillations?

____________________________________________________
Robert Cohen; 570-422-3428; www.esu.edu/~bbq
East Stroudsburg University; E. Stroudsburg, PA 18301