1 a rigid bar pivoted about a fulcrum
2 a simple machine that gives a mechanical advantage when given a fulcrum
3 a flat metal tumbler in a lever lock [syn: lever tumbler] v : to move or force, especially in an effort to get something open; "The burglar jimmied the lock", "Raccoons managed to pry the lid off the garbage pail" [syn: pry, prise, prize, jimmy]
- Rather. —Chaucer.
- For lever had I die than see his deadly face. —Spenser
- A rigid piece which is capable of turning about one point, or axis (the fulcrum), and in which are two or more other points where forces are applied; — used for transmitting and modifying force and motion. Specif., a bar of metal, wood, or other rigid substance, used to exert a pressure, or sustain a weight, at one point of its length, by receiving a force or power at a second, and turning at a third on a fixed point called a fulcrum. It is usually named as the first of the six mechanical powers, and is of three kinds, according as either the fulcrum F, the weight W, or the power P, respectively, is situated between the other two, as in the figures.
- A bar, as a capstan bar, applied to a rotatory piece to turn it.
- An arm on a rock shaft, to give motion to the shaft or to obtain motion from it.
- To move with a lever.
- With great effort and a big crowbar I managed to lever the beam off the floor.
- Compound lever: a machine consisting of two or more levers acting upon each other.
- Lever escapement: See escapement.
- Lever jack: See Jack
- Lever watch: a watch having a vibrating lever to connect the action of the escape wheel with that of the balance.
- Universal lever: a machine formed by a combination of a lever with the wheel and axle, in such a manner as to convert the reciprocating motion of the lever into a continued rectilinear motion of some body to which the power is applied.
rigid thing turning about an axis, used for transmitting and modifying force and motion
EtymologyFrom levo#Latin < levis
- present tense of leve
- present tense of leva
In physics, a lever (from French lever, "to raise", c.f. a levant) is a rigid object that is used with an appropriate fulcrum or pivot point to multiply the mechanical force that can be applied to another object. This is also termed mechanical advantage, and is one example of the principle of moments. A lever is one of the six simple machines.
Theory of operationThe principle of leverage can be derived using Newton's laws of motion, and modern statics. It is important to note that the amount of work done is given by force times distance. For instance, to use a lever to lift a certain unit of weight with a force of half a unit, the distance from the fulcrum of the spot where force is applied must be twice the distance between the weight and the fulcrum. For example, to cut in half the force required to lift a weight resting 1 meter from the fulcrum, we would need to apply force 2 meters from the other side of the fulcrum. The amount of work done is always the same and independent of the dimensions of the lever (in an ideal lever). The lever only allows to trade force for distance.
Archimedes was the first to explain the principle of the lever, stating:
"(equal) weights at equal distances are in equilibrium, and equal weights at unequal distances are not in equilibrium but incline towards the weight which is at the greater distance." Archimedes once famously remarked: "Πα βω και χαριστιωνι ταν γαν κινησω πασαν." ("Give me a place to stand and with a lever I will move the whole world.")
The point where you apply the force is called the effort. The effect of applying this force is called the load. The load arm and the effort arm are the names given to the distances from the fulcrum to the load and effort, respectively. Using these definitions, the Law of the Lever is:
- Load arm X load force = effort arm X effort force. When 2 things are balanced, when a 1 gram feather for instance is balanced by a one kilogram rock on a lever the feather would go up and the rock would go down, but if a 1 kilogram rock was balanced by a 1 kilogram rock, the lever would be in the middle.
The three classes of leversThere are three classes of levers which represent variations in the location of the fulcrum and the input and output forces.
First-class leversA first-class lever is a lever in which the fulcrum is located between the input effort and the output load. In operation, a force is applied (by pulling or pushing) to a section of the bar, which causes the lever to swing about the fulcrum, overcoming the resistance force on the opposite side. The fulcrum may be at the center point of the lever as in a seesaw or at any point between the input and output. This supports the effort arm and the load.
- Beam engine although here the aim is just to change the direction in which the applied force acts, since the fulcrum is normally in the centre of the beam (i.e. D1 = D2)
- Bicycle hand brakes
- Can opener and bottle opener
- Crowbar (curved end)
- Curb bit
- Hammer, when pulling a nail with the hammer's claw
- Hand trucks are L-shaped but work on the same principle, with the axis as a fulcrum
- Pliers (double lever)
- Scissors (double lever)
- Seesaw (also known as a teeter-totter)
- Spud bar (moving heavy objects)
- Trebuchet, an upside down example of the above picture
- Wheel and axle because the wheel's motions follows the fulcrum, load arm, and effort arm principle
Second-class leversIn a second class lever the input effort is located at one end of the bar and the fulcrum is located at the other end of the bar, opposite to the input, with the output load at a point between these two forces. Examples:
Third-class leversFor this class of levers, the input effort is higher than the output load, which is different from second-class levers and some first-class levers. However, the distance moved by the resistance (load) is greater than the distance moved by the effort. Since this motion occurs in the same length of time, the resistance necessarily moves faster than the effort. Thus, a third-class lever still has its uses in making certain tasks easier to do. In third class levers, effort is applied between the output load on one end and the fulcrum on the opposite end. Examples:
MnemonicA mnemonic for remembering the three classes of levers is the word flex, where the letters f-l-e represent the fulcrum, the load, and the effort as being between the other two, in the first-class lever, the second-class lever, and the third-class lever respectively. (To relate the mnemonic to the above diagrams, note that: the "fulcrum" is represented by the triangle, the "effort" is denoted by the arrow with a hand symbol, and the "load" is the other arrow.) To remember what the different classes of levers look like, another mnemonic is "fre 123" In a 1st class lever the fulcrum is in the middle, 2nd class the resistance is in the middle, and 3rd class the effort is in the middle of it. Alternatively, the term 'Frogs lay eggs' can also be used in the similar manner. Some people remember the word 'elf', which sorts the classes from the third to first. Another way is "FREE Lever" Which means Fulcrum + Resistance + Effort Equals Lever.
lever in Arabic: رافعة
lever in Asturian: Lleva
lever in Bulgarian: Лост
lever in Catalan: Palanca
lever in Czech: Páka
lever in Danish: Vægtstang
lever in German: Hebelgesetz
lever in German: Hebel_%28Maschine%29
lever in Spanish: Palanca
lever in Esperanto: Levilo
lever in Persian: اهرم
lever in French: Levier (mécanique)
lever in Korean: 지레
lever in Hindi: उत्तोलक
lever in Indonesian: Tuas
lever in Icelandic: Vogarstöng
lever in Italian: Leva (fisica)
lever in Latin: Vectis
lever in Lithuanian: Svertas
lever in Lojban: vraga
lever in Hungarian: Emelő
lever in Dutch: Hefboom
lever in Japanese: てこ
lever in Norwegian: Vektstang
lever in Polish: Dźwignia
lever in Portuguese: Alavanca
lever in Russian: Рычаг
lever in Simple English: Lever
lever in Slovak: Páka
lever in Slovenian: Vzvod
lever in Serbo-Croatian: Poluga
lever in Finnish: Vipu
lever in Swedish: Hävstång
lever in Telugu: తులాదండము
lever in Thai: คาน (กลศาสตร์)
lever in Turkish: Kaldıraç
lever in Ukrainian: Важіль
lever in Walloon: Djîsse (levî)
lever in Contenese: 槓桿
lever in Chinese: 杠杆
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