Question

SHM is oscillations in a straight then why angular SHM exists? What is the definition of SHM so that it can satisfy both type of SHM?

Answer 1

SHM stands for simple harmonic motion. The general definition of a simple harmonic motion is that it's a type of periodic motion where the restoring force is directly proportional to the displacement. This suits both the linear and angular SHMs, which is the ambiguity in the question. Angular SHMs are just motions that have curved trajectories (e.g. a pendulum), as opposed to linear SHMs, where the trajectory lies on a straight line.