Answer to Question #200867 in Mechanics | Relativity for Khen

Question

Explain why the motion of earth around the sun is periodic motion but is not vibratory

Answer 1

Any motion that repeats itself over and over again at regular intervals of time is called periodic motion. For example, the motion of planets around the sun.

If a body moves back and forth repeatedly about its mean position, its motion is said to be oscillatory or vibratory or harmonic motion. The swinging motion of the pendulum of a wall clock.

So every oscillatory motion is necessarily periodic but every periodic motion is not oscillatory. For example, the earth completes one revolution around the sun in one year but it does not move about a mean position. So its periodic but not oscillatory. :)

Example earth around the sun is periodic motion

But not is vibratory