1. A 20 N force is necessary to stretch a spring 0.5 m. What is the spring constant of this spring? 2. A spring has a spring constant of 25 N/m. What force is necessary to stretch the spring 0.2 m? 3. A 40 N force is applied to a spring with a spring constant of 100 N/m. How far can this spring be compressed by this force? 4. A spring with an unknown spring constant is hung vertically, and a 200 g mass is attached to the bottom. If the spring stretches 0.25 m from its resting position to the position at which the hanging mass is in equilibrium, what is the spring constant of this spring? Draw a free-body diagram for the hanging mass