A Segunda Lei da Termodinamica na formulacao da Lei de Hooke
  Hooke's Law is analyzed taking the Second Law of Thermodynamics into consideration. It is shown that the energy of a spring isn't always 1/2 k xx - this value is actually the energy of the spring plus the energy of the atmosphere that surrounds it. On a quasi-isentropic aproximation in which the dynamic force is approximately the same as the static force, k is not a constant. Only by considering an ideal spring where k is constant and only on a static regime, can we say the energy is 1/2 k xx. For any dynamic regime of such an ideal spring, the energy of the spring is a function of its temperature and therefore is different from 1/2 k xx. If any given mass is moving attached to an ideal spring, the movement will eventually cease even if such movement occurs in vacuum. The dynamic force is not the static force kx. The Second Law of Thermodynamics is essential in order to formulate Hooke's Law. 
Rodrigo de Abreu