Tensile strength is defined as a stress, which is measured as force per unit area. For some non-homogeneous materials (or for assembled components) it can be reported just as a force or as a force per unit width.
Answer Wiki. The practice of organizing to aggregate individuals' influence for economic reasons probably began with European craft guilds, although the master craftsmen were actually employers and capitalists. Trade unions or labor unions originated in England in the 1700s, but were outlawed until the 1800s.
Not soon after labor unions began to strike and cause havoc. In the 1860's, the National Labor Union was formed to unify workers in fighting for higher wages, an 8 hour work day and various social causes and it set the stage for many failing unions to come.