I've been set this question by my tutor and I'm having difficulty doing it. A mass of 2 kg is hung from the lower end of a vertical spring and extends it by 40 cm. The mass is now pulled down a further 20 cm and is then released from rest so that it oscillates about the equilibrium position. Determine : a) the spring stiffness constant k for the spring. b) the time period of the oscillations. c) the speed and acceleration of the mass when it is 15 cm from the equilibrium position. d ) the maximum speed and maximum kinetic energy of the mass. e) the maximum accelerating force on the mass. I'm struggling with it as I don't really understand how to find the K. Is the displacement 20? Or would it be 60? I think K is, F/x, x being the displacement? If someone could please explain it to me I would be very grateful. I've been out of education for some time so I'm finding some things hard to get my head around.