Engine (such as pneumatic motors), springs (clockwork motors) and elastic bands. Historic military siege engines included large catapults, trebuchets, and (to some extent) battering rams were powered by potential energy. A pneumatic motor is a machine that converts potential energy in the form of compressed air into mechanical work. Pneumatic motors generally convert the compressed air to mechanical work though either linear or rotary motion. Linear motion can come from either a diaphragm or piston actuator, while rotary motion is supplied by either a vane type air motor or piston air motor. Pneumatic motors have found widespread success in the hand-held
The Work of Art in the Age of Mechanical Reproduction free", for lacking the "aura" of the original work of art. The Work of Art in the Age of Mechanical Reproduction The Work of Art in the Age of Mechanical Reproduction (1935, "Das Kunstwerk im Zeitalter seiner technischen Reproduzierbarkeit"), by Walter Benjamin, is an essay of cultural criticism which proposes that the "aura" of a work of art is devalued by mechanical reproduction. The subject and themes of the essay have much influenced the fields of art history and architectural theory, and of cultural studies and media theory. During the Nazi régime (1933–1945) in Germany, Benjamin wrote the essay to