The law of conservation of energy states that energy cannot be created or destroyed, only transformed from one form to another within a physical system. In any process, such as mechanical work, heating, or chemical reactions, the total energy in the system remains constant, though it may change between forms like kinetic energy, potential energy, thermal energy, or chemical energy. For example, in a roller coaster, the potential energy at the highest point is converted into kinetic energy as the coaster moves down, but the total energy remains the same. This principle is fundamental in understanding and analyzing energy flow in physical systems, ensuring that energy is accounted for in all processes.