A thin metal disk of mass m=2. 00×10−3kg and radius r=2. 20cm is attached at its center to a long fiber. (figure 1)when the disk is turned from the relaxed state through a small angle θ, the torque exerted by the fiber on the disk is proportional to θ: τ=−kθ. The constant of proportionality k is called the "torsional constant" and is a property of the fiber.