Sinonimi: lever tumbler
ETYM Old Eng. levour, Old Fren. leveor, prop., a lifter, from French lever to raise, Latin levare; akin to levis light in weight, Eng. levity, and perh. to Eng. light not heavy: cf. French levier. Related to Alleviate, Elevate, Leaven, Legerdemain, Levee, Levy.
Simple machine consisting of a rigid rod pivoted at a fixed point called the fulcrum, used for shifting or raising a heavy load or applying force in a similar way. Levers are classified into orders according to where the effort is applied, and the load-moving force developed, in relation to the position of the fulcrum.
A first-order lever has the load and the effort on opposite sides of the fulcrum—for example, a see-saw or pair of scissors. A second-order lever has the load and the effort on the same side of the fulcrum, with the load nearer the fulcrum—for example, nutcrackers or a wheelbarrow. A third-order lever has the effort nearer the fulcrum than the load, with both on the same side of it—for example, a pair of tweezers or tongs. The mechanical advantage of a lever is the ratio of load to effort, equal to the perpendicular distance of the effort’s line of action from the fulcrum divided by the distance to the load’s line of action. Thus tweezers, for instance, have a mechanical advantage of less than one.
1. A flat metal tumbler in a lever lock; SYN. lever tumbler.
2. A rigid bar pivoted about a fulcrum.
3. A simple machine that gives a mechanical advantage when given a fulcrum.
1. A metal device that returns to its shape or position when pushed or pulled or pressed.
2. Device, usually a metal coil, that returns to its original shape after being stretched or compressed. Springs are used in some machines (such as clocks) to store energy, which can be released at a controlled rate. In other machines (such as engines) they are used to close valves.
3. In vehicle-suspension systems, springs are used to cushion passengers from road shocks. These springs are used in conjunction with shock absorbers to limit their amount of travel. In bedding and upholstered furniture springs add comfort.