A trolley of mass 
is held on a horizontal surface by means of two springs attached to fixed points P and Q, as shown in the figure below.
The springs, each having a spring constant 
of 
, are always extended. The trolley is displaced along the line of the springs and then released. The variation with time 
of the displacement 
of the trolley is shown in the graph below.
State and explain whether the oscillations of the trolley are heavily damped, critically damped or lightly damped.
Suggest the cause of the damping.
