Hi I was given the following problem in my coursework: 1. The problem statement, all variables and given/known data "A spring is initially compressed by 50mm when a steel ball of mass 2kg is released from just being in contact with the uncompressed spring. Determine the spring stiffness (k) of the spring." 2. Relevant equations F = mg Restorative force F = -kx 3. The attempt at a solution I gave the answer below, but the teacher has marked it as wrong. Can anyone shed any light on where I may have made a mistake? I thought it was just a simple application of Hooke's Law. F = mg F = 2 x -9.81 F = -19.62 N F = -kx 19.62 = -k(-0.05) 19.62 = 0.05k k = 19.62/0.05 k = 392.4 Thanks, any insight gratefully received.