Lever resistance (or load). It is common to call the input force "the effort" and the output force "the load" or "the resistance." This allows the identification of three classes of levers by the relative locations of the fulcrum, the resistance and the effort: These cases are described by the mnemonic "fre 123" where the fulcrum is in the middle for the 1st class lever, the "r"esistance is in the middle for the 2nd class lever, and the effort is in the middle for the 3rd class lever. The lever is a movable bar that pivots on a fulcrum attached to
Jan Lever Jan Lever Jan Lever (Groningen, 20 July 1922 - Amsterdam, 23 November 2010) was a Dutch biologist specialized in zoology, endocrinology and evolutionary biology. His ideas on evolution may be characterized as a form of theistic evolution. The Reformed Lever studied biology at Utrecht University from 1939 onwards. Lever obtained his doctorate in 1950. He served as a professor of zoology at the Vrije Universiteit Amsterdam from 1952 until 1986. In his inaugural lecture, he presented his belief that evolution was the way in which God had created the world. He further developed this argument in his book "Creatie en