Question

Every oscillatory motion is periodic but every periodic motion is not oscillatory explain ?

Answer 1

Every oscillatory motion is periodic because each oscillations in it are occurred at definite time intervals. $\quad$

E.g.: The oscillation of a simple pendulum is periodic, as it moves to and fro about the mean position for particular definite time intervals.

But every periodic motion is not oscillatory, as the to and fro motion is not found out in every periodic motion. Circular motions are periodic but not oscillatory.

E.g.: A stone tied to a rope and undergone a horizontal uniform circular motion. The motion is periodic but the stone does not appear to move to and fro about a mean position.

Answer 2

Answer:

(1) Periodic motion : A motion that repeats itself at

definite intervals of time is said to be a periodic

motion.

Examples: The motion of the hands of a clock, the

motion of the Earth around the Sun.

(2) Oscillatory motion: A periodic motion in which a

body moves back and forth over the same path,

straight or curved, between alternate extremes is

said to be an oscillatory motion.

Examples: The motion of a taut string when

plucked, the vibrations of the atoms in a molecule,

the oscillations of a simple pendulum.

[Note: The oscillatory motion of a particle is also

called a harmonic motion when its position, velocity and

acceleration can be expressed in terms of a periodic,

sinusoidal functions-sine or cosine, of time.]