work SI unit joule (J). The work done, W by a force, F is the scalar product of the force and the displacement, D s through which the force has moved.
W = F. D s (w5)
=F D s cosq
where q is the smaller angle between the force and the displacement vectors.
When the force F is not constant, the work done is evaluated by the integral
W=ò F.ds
where the displacement has taken place between the points specified by position vectors s1 and s2.
In CGS system the unit of work is erg.
1 erg = 10-7 joule
In engineering practice sometimes foot-pound (ft-lb) is used as a unit.
1 ft-lb=1 ft ´ 1 lb ´ g =1.356 J