Show that linear S. H.M is projection of a U. C.M along any of its diameter

It shows that acceleration of particle M is directly proportional to its displacement and its direction is opposite to that of displament. Thus particle M performs simple harmonic motion but M is projection of particle performing U.C.M. hence S.H.M. is projection of U.C.M. along a diameter, of circle.

c

explanation:

probably not if net force is zero