Problem:
A spring of constant k = 100 N/m hangs at its natural length from a fixed stand. A mass of 3 kg is hung on the end of the spring, and slowly let down until the spring and mass hang at their new equilibrium position.
![2123_Spring and mass hanging.jpg](https://secure.tutorsglobe.com/CMSImages/2123_Spring%20and%20mass%20hanging.jpg)
The spring is now pulled down an additional distance x and released from rest. What is the potential energy in the spring at this distance?