The principle of energy conservation states that energy can neither be created nor destroyed, but can only change forms. This concept is based on the law of conservation of energy, which is also known as the first law of thermodynamics. According to this law, the total amount of energy in a closed system remains constant over time.

Energy conservation can be observed in various systems. For example, when a pendulum swings back and forth, the potential energy at the highest point is converted into kinetic energy as it moves downward. Likewise, when the pendulum reaches its highest point again, the kinetic energy is converted back into potential energy.

Another example is a roller coaster ride. As the coaster reaches the top of the first hill, it has maximum potential energy. As it descends, the potential energy is gradually converted into kinetic energy due to the force of gravity. At the bottom of the hill, the potential energy is at its minimum, while the kinetic energy is at its maximum.

In both of these examples, it is evident that energy transformation occurs while the total energy of the system remains constant. This principle is crucial to understanding the behavior of energy in various natural and artificial systems.