Practice: Hooke's Law & Elastic Potential Energy 1) A spring is stretched 6 cm when a mass of 200 g is hung on it. Calculate the spring constant of this spring. 2) If a spring has a spring constant of 2 N/m and it is stretched 5 cm, what is the force of the spring? 3) A trampoline has a spring constant of 3430 N/m. How far will the trampoline sink when a 70 kg person steps on it? 4) A force of 200 N stretches a spring 30 cm. What is the spring constant of the spring? How far would this spring stretch with a force of 100 N applied to it? 5) A 20 kg box is attached to a compressed spring that has a spring constant of 300 N/m. The box is resting on a frictionless surface and the spring is compressed 30 cm. What is the elastic potential energy of the spring? 6) A spring has a spring constant of 256 N/m. How far must it be stretched to give it an elastic potential energy of 48 J? 7) What is the spring constant of a spring if it has 55 J of stored elastic energy when it is compressed 35 cm? 8) A 375 g mass is hanging from a vertical spring. The spring constant is 2125 N/m. What is the stored potential energy? (Hint: find the stretch first)