# simple harmonc motion

distance between two particles at any time t =| A(sin(wt+a)-sin(wt))|

=A*|2sin(a/2)cos((2wt+a)/2)|

max value is when |cos((2wt+a)/2)|=1

max distance=2A|sin(a/2)|=20cm=A; or, |sin(a/2)|=1/2

or, sin(a/2)=1/2 or -1/2,

a/2=pi/6 rad or -pi/6 rad

a = pi/3 rad or -pi/3 rad.

therefore SHMs have a phase difference of pi/3.