After 1.0 N stone is hung from the end of a long light spring (k = 1.50 N/m) the system oscillates up and down with SHM. When you stop the stone from bouncing up and down, and set it into small amplitude motion as a PENDULUM, its frequency of oscillation is ½ that of when it was bouncing. What is the unstretched length of the spring, i.e. before the stone was hung on it?