Mechanical work or work (symbol: A or W) is a physical quantity that describes the effort expended in changing a situation and is equal to the dot product of force and the displacement vector of the body moved under the influence of the force:
$$W = \vec{F} \cdot \vec{d}$$
where,
F— force;
d— displacement.
If a force acts at an angle α to the direction of motion, work can be found using the formula:
$$W = F \cdot d \cdot \cos \alpha$$
Unit of work in the SI system is joule (J).
Work is positive when the force is in the direction of motion, aiding the motion. Work is negative when the force is opposite to the direction of motion, resisting the motion.