1. The problem statement, all variables and given/known data Figure 8-36 shows an 8.00 kg stone at rest on a spring. The spring is compressed 10.0 cm by the stone. (a) What is the spring constant? 2. Relevant formula Mechanical energy is conserved 3. The attempt at a solution The decrease in gravitational potential energy that occurs when the block is put on the spring (the spring is compressed) is equal to the increase in elastic potential energy of the spring. Thus: mgh=0.5kh^2 (the coordinate system is chosen so that gravitational potential energy is zero when the block is at rest and the spring is compressed) Solving the equation for k gives k=2gm/h k=2*9.8*8.0/0.1=1568 N/m. Yet, the answer turns out to be 784N/m :/ What did I do wrong? Thanks!