We investigate nonlinear springs. A spring is linear if it obeys Hooke’s Law, which indicates that the applied force to stretch the spring is F(x) = kx. For a linear spring, F     is constant. If, instead, F' is not constant, then the spring is called nonlinear. Furthermore, if F' (x) increases as x increases, then the spring is said to be progressive, and if F' (x) decreases as x increases, then the spring is said to be degressive.

Of the two statements (a) and (b), which describes a progressive spring, and which describes a degressive spring?

(a) To stretch the spring a fixed additional distance, a greater change in force is needed farther from equilibrium than closer to it.

(b) To stretch the spring a fixed additional distance, a greater change in force is needed closer to equilibrium than farther from it.