1. The problem statement, all variables and given/known data The energy change of a oscillating spring. It involves SHM and the energy involved are GPE, KE and Elastic PE (EPE). 3. The attempt at a solution I understand the other conversions e.g. On the downward journey above the equilibrium position, the gravitational p.e. is changed to elastic p.e. and k.e. But there is one part I dont understand: On the upward journey above the equilibrium position, the k.e. and elastic p.e. are changed to gravitational p.e. Shouldnt there be elastic PE when it is compressed as in 'compressed energy'? ( k.e. changed to EPE and GPE) or is there a gross misunderstanding on my part? In hooke's law, the 'x' means extension but does it count compression distance? Thanks.