Final answer:
The force exerted by a spring is directly proportional to the square root of the spring stiffness according to Hooke's law.
Step-by-step explanation:
The question pertains to the relationship between force and stiffness of a spring. According to Hooke's law, the force exerted by a spring is directly proportional to the displacement from its equilibrium position. In this case, the question states that the same force is required to stretch the spring a distance x as to stretch it twice as far. This means that the force exerted by the spring is proportional to the square root of the spring stiffness.