What is the SI unit of energy or work?

The SI unit of energy or work is the Joule. This unit is defined as the amount of work done when a force of one newton acts through a distance of one meter. It can also be understood as the energy transferred when one coulomb of electric charge is moved through an electric potential difference of one volt.

The Joule is named after James Prescott Joule, who studied the relationship between heat and work, demonstrating that energy can be transformed from one form to another. In practical terms, the Joule is the standard unit used in various scientific fields to quantify energy, such as in physics and engineering, making it a fundamental component in the study of energy and work.

In contrast, other units mentioned are associated with different physical concepts: the Watt measures power (energy per unit time), the Newton measures force, and the Kilogram measures mass. Thus, the Joule specifically pertains to energy and work.