Periodic motion is any motion that repeats itself (same position and velocity).

An oscillation is a special case of periodic motion though a central point, typically an equilibrium location (zero net force location).

Simple harmonic motion (SHM) is a special case of an oscillation where the net force is proportional to displacement and the position as a function of time is a sine or cosine function.

A rock dropped into a bucket of water is an example of...

A) periodic motion that is not an oscillation

B) an oscillation that is not simple harmonic motion

C) simple harmonic motion

D) none of the above

Solution: D. A rock dropped into a bucket of water will simply sink to the bottom. It will not repeat its motion.