In common language, work refers to activities requiring physical or mental strength and effort. A person’s daily work may include studying for an exam, playing the flute or thinking through a meticulous business plan. Work can also refer to an activity performed for pay or to achieve a goal, such as writing an article or running a race. It may also refer to a person’s work-life balance, including balancing family obligations and career responsibilities.
Scientifically, however, work is a physical quantity related to the transfer of energy. The SI unit of work is the joule (J), named after 19th-century English physicist James Prescott Joule. The magnitude of work is calculated by multiplying a force and a displacement, or an object’s change in position. The relative directions of the force and displacement determine whether the work is positive, negative or zero.
When an object is displaced by a force, the work done is equal to the force multiplied by the distance displaced. In addition, a vector quantity, work can also be described as the dot product of a force and a displacement. For example, the work done when a 10 Newton force causes an object to move through a displacement of 2 meters is 10 N * (2 m) = 20 J.
Similarly, the work done by a gravity on an object falling from a certain height is equal to the mass of the object times its acceleration. Since gravitational energy is a form of potential energy, the gravitational work done is positive.
Other forms of energy that can be changed by work include the kinetic energy of a moving object and the thermal or electrical energy in a system. In a mechanical device, work can also change the potential energy into kinetic energy, and vice versa.
In a more general sense, the term work can also refer to any activity that is undertaken to change something into a different state or condition. For instance, the process of transforming coal into a fuel, oil into gasoline and gold into jewelry is often considered to be a type of work. Similarly, the act of performing surgery on a patient or the process of gaining knowledge are often considered to be types of work.