Work

(würk.) [A. S. worc.] (Mech.) A force is said to do work when it moves the body to which it is applied, and the work is measured by the product of the resistance overcome into the space through which it is overcome. The amount of work done in raising a weight does not depend only on the weight, but also on the space through which it is lifted. When work is done by means of a machine, the work done at the one extremity is exactly equal to that applied at the other, pa ive resistances, such as friction, being neglected. Thus, if we consider a lever with arms 4ft. and 1 foot respectively, we find that a power of 1 Ib. will support a weight of 4 lbs., but if the weight be raised 1 foot, the power must descend through 4 feet, so that the work done at the two extremities of the lever is the same. If a force always acts in a direction perpendicular to the direction of motion, it does no work; thus the pre ure of the horizontal plane on which a stone is rolling, the tension of a cord to which a pendulum-bob is attached, the attraction of the sun on a body describing a circle about the sun as centre, are all examples of forces which do no work. See MACHINE. [s. 968]