English: Graph of the potential energy of a conservative bistable system. There are two local minima of the potential energy at x₁ and x₂ which are stable equilibrium points at which the red object can rest. Between them is a local maximum of energy x₃ which is an unstable equilibrium point. If the red object is placed there it is in equilibrium but unstable; the slightest disturbance will cause it to move to one of the stable equilibrium points