Question

1. All oscilatory motions are periodic but all periodic motions are not oscillatory. Explain it.

Answer 1

Periodic motion are those which repeats itself after particular interval of time.
Ex: motion of planet around sun.
Oscillatory motion are those in which particle performs to and fro motion about the mean position and repeats its motion after particular interval of time.
Ex: simple pendulum.

All Oscillatory motions are periodic but converse is not true because all periodic motion do not perform to and fro motion.
Like planet while revolving around the sun do not perform to and fro motion but simple pendulum does.
Both are periodic but not oscillatory.