SPRING FORCE ( HOOKE'S LAW)

Spring Force - Hooke's Law

Fs
= Force exerted by the spring. SI: N

k
= Spring Constant. SI: N/m




x
= Displacement from equilibrium position. SI: m



* The negative sign indicates that the spring force is a restoring force, i.e. the force Fs always acts in the opposite direction from the direction in which the system is displaced.

* The origin has to be placed at the position where the spring system would be in equilibrium for the equation Fs= -k x to be valid. This is the location where the net force on the object to which the spring is attached is equal to zero. If not, then Fs= -k (x - xo) where xo is equilibrium position relative to the origin.

*Springs are normally assumed to be massless so that their inertia can be neglected. This also means that the forces exerted by both ends of the spring are the same but in opposite directions.

*Had the direction for the positive values of x been taken to the left rather than the right then Fs= k x. To avoid confusion we will always take the direction for positive values of x in such a way that Fs= -k x.