Work may be described as any purposeful activity undertaken for remuneration, or by an individual or group. It can involve physical and/or intellectual exertion, as in work requiring strenuous or tiring effort, such as a demanding job or sport. The words work, labor, travail, drudgery, grind, and sweat all suggest arduous or unpleasant effort. Work may be accomplished by an individual, a machine, or a natural force. Work can also be a metaphor for the activities of life and may refer to career, calling, or business.
Generally speaking, to do work means to apply force over a distance and cause a displacement of an object, or a change in position. If the direction of the displacement is parallel to the direction of the force, then the work done is positive. If the direction of the force is opposite to the direction of the displacement, then the work done is negative. The SI unit for measuring work is the joule, which is the same as the energy unit (see energy).
When an object is at rest, it has no potential energy and thus does not do any work. However, when a force is applied to an object and the displacement changes direction, then the work done is the same as the amount of energy that was transferred from the object to the force, or the energy that was added to the object. This is called conservation of linear momentum, or kinetic energy.
If the direction of the force is perpendicular to the motion of the object, then the work done by that force is zero. If the direction of the force is parallel to the motion of the object, then the object does not do any work. A good example of this is when a ball is dropped by gravity – the gravitational work done on the ball is equal to its weight multiplied by the distance to the ground.
A more complicated case is when the force exerted on the object has a component that causes a change in direction of the displacement but a smaller component that causes a change in position of the displacement. This is called frictional work and can be either positive or negative. For example, when a person holds a heavy load down on a steep hill to prevent it from sliding down the hill, the force exerted is large but the displacement and position change are small, so no work is being done.
Work is an important part of our daily lives and can have a huge impact on our lives. It can contribute to our health, our self-esteem and our sense of identity, especially if the job is fulfilling. It can also help keep our economy moving as money is exchanged for goods and services, allowing us to buy things we need or want. It can also make us feel good about ourselves and others, providing meaning and purpose in our lives.