For a spring the deformation strain produced by a force stress is proportional to the force applied as long as its elastic limit is not exceeded so the spring can return to its original shape after the force is removed Thus where is the force due to the weight of the mass is the displacement from the equilibrium position and is the force constant depending on the material used the number of windings and so on The deformation can also be a compression for negative The plot on the right shows displacement as a function of mass for fixed This law was discovered in 1676 by the British scientist Robert Hooke