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.
The first Labor Day was held in 1882. Its origins stem from the desire of the Central Labor Union to create a holiday for workers. It became a federal holiday in 1894. It was originally intended that the day would be filled with a street parade to allow the public to appreciate the work of the trade and labor organizations. After the parade, a festival was to be held to amuse local workers and their families.