One end of a light spring of spring constant k is fixed to a wall and the other end is tied to a block placed on a smooth horizontal surface. In a displacement, the work done by the spring is 1/2 kx2 . The possible cases are
(a) the spring was initially compressed by a distance x and was finally in its natural length
(b) it was initially streched by a distance x and finally was in its natural length
(c) it was initially in its natural length and finally in a compressed position
(d) it was initially in its natural length and finally in a stretched position.
