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
Mark A. Lever crust. Mark A. Lever Dr. Mark Lever (born 1977) is a microbial ecologist who studies the role of microorganisms in the global carbon cycle. He is a professor of environmental microbiology in the Department of Environmental Systems Science in the Institute of Biogeochemical and Pollutant Dynamics at ETH Zurich. Dr. Lever earned his MA in Marine Biology at the Boston University Marine Program at Woods Hole in 2002 and his PhD in Marine Sciences at the University of North Carolina, Chapel Hill in 2008. He worked as a postdoctoral scientist at Aarhus University from 2009 to 2014, when he joined