Hooke’s law is a principle of physics that states that the force F needed to extend or compress a spring by some distance x is proportional to that distance. That is: F = -kx, where k is the stiffness of the spring. In other words, the stiffer the spring the more force you require to pull/push it and vice versa.
F ({{ -main.k * main.x / 100 | number: 0 }}) =
*
x ({{ main.x | number: 0 }})