A metal block hangs vertically from one end of a spring. The other end of the spring is tied to a thread that passes over a pulley and is attached to a vibrator, as shown in the figure below.
The vibrator is switched off. The metal block of mass 
is displaced vertically and then released. The variation with time 
of the displacement 
of the block from its equilibrium position is shown in the figure below.
Calculate the angular frequency 
for the vibrations of the block.
.
