As an engineering undergrad, I refer to "cyclic motion". My friend, an arts student, uses the term "cyclical unemployment" (whatever that means) instead.
The only article I can find on the web about this didn't reach any conclusion except that words with -ic and -ical endings were normally the same, but occasionally the language has evolved to use them in different contexts (for example most people would see a difference between "magic" and "magical") [contrapunctus.net].
Is this divide entirely just convention in respective subjects?