LEV'ER, n. [L. levo, to raise.] In mechanics, a bar of metal, wood, or other substance, turning on a support called the fulcrum or prop. Its arms are equal, as in the balance; or unequal, as in steelyards. It is one of the mechanical powers, and is of three kinds, viz. 1. When the fulcrum is between the weight and the power, as in the handspike, crowbar, &c. 2. When the weight is between the power and fulcrum, as in rowing a boat. 3. When the power is between the weight and the fulcrum, as in raising a ladder from the ground, by applying the hands to one of the lower rounds. The bones of animals are levers of the third kind.
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