## Definitions and concepts of lever

### Definition of lever

The lever is a simple machine that function is to transmit a force and a displacement. It is composed by a rigid bar that can be freely rotated around a point called the fulcrum.
It can be used to amplify the mechanical force applied to an object, to increase your speed or distance traveled, in response to the application of a force.
The discovery of the lever and its use in daily life comes from prehistoric times. Their daily life, in the form of grooved employment, is documented since the third millennium BC - in cylinder seals from Mesopotamia - up to our days. The oldest manuscript which is preserved with a mention of the lever is part of the synagogue or mathematical collection of Pappus of Alexandria, a work in eight volumes estimated was written around the year 340. There appears the famous remark of Archimedes:
"Give me a fulcrum and I will move the world."
Attributed to Archimedes helenus the first formulation of the mathematical principle of the lever.
Acting forces
Three forces acting on the rigid bar which constitutes a lever:
• The power; Q: is the force that we voluntarily apply in order to obtain a result; either manually or through other mechanisms or motors.
• Resistance; A: is the force which we overcome, exerted on the lever by the body to move. Its value is equivalent, by the principle of action and reaction, the force transmitted by the lever to that body.
• The strength of support: is the exercised by the fulcrum on the lever. If the weight of the bar is not considered, it will always be equal and opposite to the sum of the previous ones, in order to keep the lever without moving the point of support, on which rotates freely.
• Arm of power; BP: the distance between the point of application of the force of power and supporting point.
• Arm of resistance; BR: distance between the tensile strength and the support point.

### Concept of lever

The man, from the beginning of time has devised mechanisms that allow you to save energy and thereby make their physical efforts increasingly smaller.
The various mechanisms to make more efficient efforts include the pulleys, gears and levers.
The lever is a simple machine that is used in a wide variety of applications.
Probably, even, the levers are one of the first engineered mechanisms to multiply forces. Thing to imagine placing a large rock as a door to a cave or upside down, remove large rocks to enable a cavern.
With a good lever it is possible to move the larger weights and also those posed by being so small also difficulty to treat them.
There is the own Archimedes, in its studies on the levers, I would have said: "Give me a fulcrum and I will move the world". In fact obtained that support point and using a lever sufficiently long, that is possible.
In our daily life are many times that "we are making lever". Since moving a finger or an arm or a foot up to take the spoon to drink soup involves leverage of one form or another.
Not to mention more obvious how to play seesaw, things do operate a scale, use a nail Clipper, scissors, a little devil (crowbar), etc.
Almost as long as he wondered about the usefulness of a lever, the answer goes by the side that "serves to multiply a force", and that is true but prevailing sense that multiply is to increase, and sometimes is not so always, multiplying is lower (think of multiply by a decimal number, for example).
What is a lever?
Basically consists of a rigid bar, a point of support (you can be called "fulcrum") and the two forces (minimum) present: a force (or resistance) to which must be overcome (usually a weight to hold or lift or move in general) and force (or power) that applies to perform the action that is mentioned. The distance between the fulcrum and the place where each force, in the rigid bar, is applied is called arm. Thus, each force a true arm corresponds to.
In almost all cases of simple machines, with the lever it's overcome an element, located at one end of the bar, applying a force of smaller value that is called power, at the other end of the bar.
In a lever we can then distinguish the following elements:

### Definition of lever

A Greek word which can be translated as "garrote" derived the Latin palanga. This term, with time, became lever, a simple machine that allows you to move objects from the transmission of a force.
The lever is formed from a baluster that located on a support point, can rotate about this. By applying force on one end of the lever, it is possible to move a body, raise, etc.
For example: "We will have to use a lever to open the door is jammed", "With the help of a lever, the young man got lift trunk and rescue dog", "When I was little, I used to assemble a lever for throwing stones at the river".
The basic elements that Act on a joystick are the power, resistance and the strength of support. The force applied in manual or automatic way over the bar is the power, while resistance is the force exerted by the object in question on that toolbar. The strength of support, the last is which exerts the point of support (known as fulcrum) on the device.
The distance that exists at the point where the power is applied and the fulcrum is named debrazo of power, while the gap in the resistance and the fulcrum point is called the arm of resistance.
In automobiles, the shift lever allows through various relationships that occur in the gearbox of a March to another. In general, this lever is located between the seat of the person who leads and your passenger seat.