The force of a spring, the more you stretch or compress a spring the greater the force of the spring. Hooke's law tells us the force of a spring is equal to -kx. The K is the spring constant, the stiffness of the spring and the x is the displacement from equilibrium. We also learned what elastic potential energy is, which is the work done in stretching or compressing the spring. The equation of elastic potential energy is (1/2)kx^2. A spring with a spring constant of 4N/m is compressed by a force of 1.2 N. What is the total elastic potential energy stored in the compressed spring? We first have to find the displacement of the spring. We rearrange the force of a spring formula so that x=Fs/-k. We divide 1.2 N by -4 N/m and we get -.3m. Then we take our x and we plug it into the equation (1/2)(4 N/m)(-.3m)^2 and we get .18 J.