Answer:
The joule (symbol: J) is the SI unit of work and energy because it is defined in terms of other base SI units. Specifically, one joule is defined as the amount of work done or energy required when a force of one newton (N) is applied over a displacement of one meter (m) in the direction of the force. This can be expressed as:
1 joule = 1 newton × 1 meter
or
1 J = 1 N⋅m
The newton, in turn, is defined as the force needed to accelerate one kilogram (kg) of mass at a rate of one meter per second squared (m/s²). So, the joule is ultimately derived from the base SI units of kilogram, meter, and second.
Using the joule as the standard unit for both work and energy emphasizes the fundamental relationship between these two concepts. In physics, work is done when a force is applied to an object, causing it to move in the direction of the force. The energy transferred to the object through this process is equal to the work done.
By defining the joule in terms of base SI units, it allows for consistent and coherent measurements of work and energy across various scientific and engineering fields, making it easier to compare and convert between different units and systems.