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.
Beginning in the late 19th century, as the trade union and labor movements grew, a variety of days were chosen by trade unionists as a day to celebrate labor. In the United States and Canada, a September holiday, called Labor or Labour Day, was first proposed in the 1880s. In 1882, Matthew Maguire, a machinist, first proposed a Labor Day holiday while serving as secretary of the Central Labor Union (CLU) of New York.