Hello. I come across a problem: how to calculate the partition function of a classical spring whose energy is 1/2kx^2, and use thermodynamics to show that the force on the spring is linearly proportional to its elongation x? I got stuck at the first step. What is the energy of the spring, is it (1/2)kx^2 or (1/2)(p^2/2)+(1/2)kx^2? Really confused. Thanks in advance for answering the question!