Which law states that energy cannot be created or destroyed?

The Law of Conservation of Energy is fundamental in physics and states that the total energy in an isolated system remains constant, meaning that energy can neither be created nor destroyed but can only change forms. For instance, when energy is converted from one type to another—such as kinetic energy to potential energy during a roller coaster's ascent—the total energy remains unchanged throughout the process. This principle is crucial in understanding various scientific phenomena, from simple mechanical systems to complex biochemical reactions.

The other choices relate to different principles: The Law of Motion pertains to the movement of objects; The Law of Gravity describes the attraction between masses; and The Law of Thermodynamics involves energy transfer and transformation, including concepts of heat and work, but does not solely address the conservation of energy.