Forces with levers :
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Fe = Fl dl / de (1)
where
Fe = effort force (N, lb)
Fl = load force (N, lb) (note that weight is a force)
dl = distance from load force to fulcrum (m, ft)
de = distance from effort force to fulcrum (m, ft)
http://www.explainthatstuff.com/toolsmachines.html
http://www.engineeringtoolbox.com/levers-d_1304.html
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