Question

Why all oscillatory motions are not periodic?

Answer 1

All oscillatory motions are periodic because each oscillations gets completed in a definite interval of time. Eg: On being pulled and then released, a load attached to a spring executes oscillatory motion. On the other hand, all periodic motions may not be oscillatory. Eg: Revolution of planets around the Sun is a periodic motion but not an oscillatory motion (i.e. no to and fro motion about its mean position is present).