Energy can exist in numerous forms, such as chemical, electrical, kinetic, potential, mechanical, thermal, and nuclear, and their sum constitutes the total energy E of a system. The total energy of a system per unit mass is denoted by e and is defined as
Where:
- e is the specific energy in joules per kilogram (J/kg),
- E is the total energy in joules (J), and
- m is the mass in kilograms (kg).