@Tech-With-Us instead of potential energy we take consideration the work done by gravity
@aarushi-kalia (no. Of elements in set of first term) X ( no. of elements in set of common difference) = Ans i.e. 15
@Ilham-Syed the pulley is massless thus it doesn't have moment of inertia.
It is a question of NLM
Try it you'll get a=g/3
@Yash-malviya ya wrote it by mistake