F — restoring force (N) k — spring constant (N/m) x — displacement (m) PE = ½kx²
Spring state
at rest
k · spring constant200 N/m
x · displacement0.0 m
F = −kx0.0 N
PE = ½kx²0.0 J
|x| / x_max0%
F
0 N
PE
0 J
F = −kx · force opposes displacement
PE = ½kx² · energy stored
double x → double F, quadruple PE
k is stiffness — bigger = stiffer
F = −kx: drag the displacement slider. The restoring force always points back toward equilibrium — that's what the negative sign means. The spring always fights back.