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.
(i) It is periodic but not S.H.M. because it is not to and fro motion about a fixed point.
(ii) It is S.H.M.
(iii) It is S.H.M.
(iv) It is a periodic but not S.H.M. A polyatomic gas molecule has a no. of natural frequencies and its general motion is the resultant of S.H.M. of no. of different frequencies and its general motion is the resultant of S.H.M. of no. of different frequencies. The resultant motion is periodic but not S.H.M.