What is Periodic Motion : In Physics, a motion that is regular and repeating is called Periodic Motion. The time to complete one full motion is called the Time period of the Periodic Motion
What is SHM: A Simple Harmonic Motion is a special case of Periodic motion where a physical quatity varies sinusoidally.In this Periodic motion the restoring force is directly proportional to the displacement. The object oscillates between two position and Motion is sinusoidally in nature.

A non inertial Frame of Refrence is the frame of refrence which is having acceleration a. Example Free Falling elevator
Newtons law are valid in inertial frame of refrence only. We cannot apply them as it is in non inertial frame of refrence as it left out the acceleration of the object because of the frame of refrence.
Let me provide simple example to illustrate this.

All students preparing themselves for JEE Main 2025 should have already started their preparation from class 11. The simple mantra for success here is to have the complete knowledge of JEE Main 2025 Syllabus. It’s not easy to cover the entire syllabus within the time for most of the students as most of them start