Graph for the potential energy of a couple of functions (same as in chapter 3 paragraph 10 of our book). [list] [*] If the checkbox is unchecked, the plotted potential energy (blue) is that of a spring. The abscissae correspond to the amount of elongation ([[math]x>0[/math]] or compression ([[math]x<0[/math]]. [*] The abscissae correspond to the amount of elongation ([[math]x>0[/math]] or compression ([[math]x<0[/math]]. [*] If the checkbox is checked, a different plot is shown. The corresponding system has three equilibrium points (two stable and one unstable). [*] Total mechanical energy can be varied by moving the point on the energy axis. [*] The point on the energy curve signals the situation of the system. Two segments show the potential (blue) and kinetic (red) energy of the system. [*] Physical situations correspond to potential energies less than the total energy. Outside this region the kinetic and potential "bars" disappear, and the point on the curve becomes black. [/list]