Mechanical energy is the sum of potential energy and kinetic energy in a system. Potential energy is stored energy based on an object's position, while kinetic energy is the energy of motion. For example, a stretched rubber band has potential energy, and when released, it converts that energy into kinetic energy as it moves. Mechanical energy is important in various applications, such as in machines and vehicles. These systems rely on mechanical energy to perform work, like lifting objects or moving from one place to another. Understanding mechanical energy helps in designing efficient systems and improving energy use in everyday life.