Q. In one dimension, it is obvious that the force obeying Hook's law is conservative. Consider instead a spring that obeys Hook's law and has one end fixed at origin, other than whose other end is free to move in all 3 dimensions. (The spring could be fastened to a point in the ceiling and be supporting a bouncing mass m at its other end, for instance) Write down the force F(r) exerted by the spring in terms of its length r and its equilibrium length r0. Prove that this force is conservative.