高一物理 請指教

A stretched spring obeys Hooke's Law if and only if its extension is within the elastic limit. The law fails in case the spring is stretched by a force to have an extension outside the elastic limit. Therefore, it is no applicable to ANY FORCE.
Within the elastic limit, the applied force F and extension x are proportional, i.e.
F = kx
where k is the spring constant (or force constant)

i dont quite understanding what you are saying, but


F= (k*x*x)/2