As you watch, focus on the bar at the top of the screen. It will show that the total amount of energy in the system (the roller coaster) never changes, as the bar's length stays the same all of the time. However, the kind of energy changes throughout... That is the law of conservation of energy! Energy cannot be created or destroyed, but it can change from one form to another. In this example, the energy goes from potential to kinetic to dissipated as the roller coaster moves along the track.