1. The problem statement, all variables and given/known data A spring has a relaxed length of 7 cm and a stiffness of 50 N/m. How much work must you do to change its length from 12 cm to 16 cm? 2. Relevant equations 1/2*kss2 3. The attempt at a solution 1/2*50*(.16-.12)2 = 0.04 It shows the solution to be 0.14. It says the change in the energy of the spring is its change in potential energy, so the change in (1/2)kss2. Be sure to use the stretch s, not the length, and use meters, not centimeters.