# Work (physics)

In physics, work is the amount of energy transferred by a force.

Like energy, it is a scalar quantity, with SI units of joules. Heat conduction is not considered to be a form of work, since there is no macroscopically measurable force, only microscopic forces occurring in atomic collisions. The term work was created in the 1830s by the French mathematician Gaspard-Gustave Coriolis.[1]

According to the work-energy theorem if an external force acts upon a rigid object, causing its kinetic energy to change from Ek1 to Ek2, then the mechanical work (W) is given by:[2]

$W = \Delta E_k = E_{k_2} - E_{k_1} = \frac{mv_2^2}{2} - \frac{mv_1^2}{2}$

where m is the mass of the object and v is the object's velocity.

If a force F acts on an object while the object is displaced a distance d, and the force and displacement are parallel to each other, the work done on the object is the product of F and d:[3]

$W = F \cdot d$

If the force and the displacement are in the same direction, the work is positive. If the force and the displacement are in opposite directions the work is negative.

## References

1. Jammer, Max (1957). Concepts of Force. Dover Publications, Inc.. ISBN 0-486-40689-X.
2. Tipler (1991), page 138.
3. Resnick, Robert and Halliday, David (1966), Physics, Section 7-2 (Vol I and II, Combined edition), Wiley International Edition, Library of Congress Catalog Card No. 66-11527