Hi everyone! So I'm kind of new to physics forums but I've been having a major problem with this scenario and I can't figure it out. Its not exactly a direction question but more of a situation that doesn't make sense to me... Say we have a spring that's hanging vertically. And we say we attach a mass at the end of the spring and the spring stretches to maximum extension. According to Hooke's Law, the force exerted by the spring (Fx) is proportional to the extension of the spring. So Fx=kx. In addition, the force exerted by the spring is equal (but in the opposite direction) to the force applied on the spring. Following this situation, we would assume the force exerted on the spring is the Fg of the hanging mass, which would be equal to mg. Therefore, the restoring force of the spring should be equal to the Fg of the mass (mg). However, when I work out the problem in terms of energy equations, it appears that the restoring force is actually double the Fg exerted by the object. However, My question is this.... how can we prove that the restoring force is double the force exerted by the hanging? Or, am I just doing something incorrect in my energy calculations. Thanks!