What does it mean to say that "an exactly equivalent way to express Hooke's Law is by the potential energy"? From Taylor, _Classical Mechanics_ ![enter image description here]( What does that last line mean? Force and energy do not have equivalent units, so I don't understand how the author relates them. Intuitively, I can see how both the force and the potential energy _oscillate_ , but other than that I'm not sure what mathematical connection there is.

Surely you are familiar with: $-\
abla U(x)=F(x)$.