The variation of velocity of a particle executing SHM with time is shown in figure. The velocity of the particle when a phase change of takes place from the instant it is at one of the extreme positions will be
From the graph T = (5 -1) = 4 s
(distance between the two adjacent crests shown in the figure)
The equation of velocity can be written as
Phase of the particle velocity at that instant corresponding
to the above equation = .
Therefore, when a phase change of /6 takes place, the
resulting phase = +/6.