Question

The motion which repeats itself after a fixed interval of time.

Answer 1

Periodic motion that repeats itself after a fixed and regular period of time. They are often termed as harmonic motion as they take place at regular interval. To do this the object should be in stable position.

The direction of the force also needs to be towards the equilibrium and the resistive force in the path like the friction should be negligible, or the motion of the object will stop. 

Answer 2

Answer:

The motion which repeats itself after a fixed interval of time is known as periodic motion.