Theory: (such as a spring) Materials can behave in different ways when a force is applied to them.in this case the relationship between the restoring force F and the displacement from equilibrium position x is given as follows F=kx For springs this relation is known as Hooke's Law Here F is the force on the spring.Consider a spring that extended some distance by an effect of force, when applied different weights to springs and found that the extension of a spring is proportional to the force applied.The unit for the spring constant is newtons/meter.