palancas

Palancas, known in English as levers, are simple machines consisting of a rigid bar that pivots around a fixed point called a fulcrum. By arranging the fulcrum and the points where forces are applied, a lever can modify either the force or the distance over which it acts.

The mechanical advantage of a lever is given by the ratio of the input arm length to the output arm length. In an ideal lever, the work done on the input side equals the work delivered to the load, so a larger force is achieved at the expense of travel distance.

Levers are categorized into three classes depending on the relative positions of the fulcrum, the effort, and the load: Class I has the fulcrum between effort and load (for example, a see-saw); Class II places the load between the fulcrum and the effort (for example, a wheelbarrow); Class III places the effort between the fulcrum and the load (for example, a fishing rod or tweezers).

Levers are among the earliest recorded simple machines. Archimedes described their power and reportedly said, Give me a lever long enough and a fulcrum on which to place it, and I shall move the world.

In nature and technology, palancas are used to change the magnitude or direction of forces. In biomechanics, bones and joints act as levers, while in machinery, levers are embedded in tools, clamps, and control mechanisms to reduce effort or increase speed.