Which of the following examples represent
(nearly) simple harmonic motion, and which represent periodic but not S.H.M.:
(i) The motion of earth about its axis.
(ii) Motion of an oscillating mercury column in a U-tube.
(iii) Motion of a ball bearing inside a smooth curved bowl when released from a point slightly above the lowermost position.
(iv) General vibration of a polyatomic molecule about its equilibrium configuration.