Which unit is used to express energy in the International System of Units?

The unit used to express energy in the International System of Units (SI) is the joule. One joule is defined as the amount of energy transferred when one newton of force is applied over a distance of one meter. This relationship highlights the connection between energy, force, and distance, making joules a fundamental unit in physics.

In addition to joules, other units mentioned in the options represent different physical quantities. The calorie, for instance, is a unit of energy but is not part of the SI system; it is often used in the context of food and nutrition. The newton is a unit of force, measuring the amount of force required to accelerate one kilogram of mass by one meter per second squared. The watt, on the other hand, is a unit of power, representing the rate at which energy is transferred or converted, rather than the energy itself. Thus, joules serve as the standard unit for measuring energy in the International System of Units.