http://en.wikipedia.org/wiki/Pulley

A pulley, also called a sheave or a drum, is a mechanism composed of a wheel on an axle or shaft that may have a groove between two flanges around its circumference.[1] A rope, cable, belt, or chain usually runs over the wheel and inside the groove, if present. Pulleys are used to change the direction of an applied force, transmit rotational motion, or realize a mechanical advantage in either a linear or rotational system of motion. It is one of the six simple machines. Two or more pulleys together are called a block and tackle.


http://en.wikipedia.org/wiki/Block_and_tackle

http://ciencia.hsw.uol.com.br/sistema-de-roldanas.htm

"pulley" é roldana; "block and tackle" é talha

WHAT IS A BLOCK AND TACKLE? Veja foto

A block and tackle is two sets of pulleys linked by a single rope. Pulling the rope draws the block and tackle together. This magnifies the effort put in so that you can lift or lower a heavy load—a car engine, for example. Block and tackle pulley systems have been used for centuries to raise sails and shift cargo on sailing ships.
http://www.factmonster.com/dk/encyclopedia/machines.html

A block and tackle[1][2] is a system of two or more pulleys with a rope or cable threaded between them, usually used to lift or pull heavy loads. The block and tackle pulley was probably invented by Archimedes[
http://en.wikipedia.org/wiki/Block_and_tackle

Talha Exponencial Veja foto

A talha exponencial, composta de um sistema de roldanas, é uma máquinas simples. As roldanas fixas podem ser observadas no ponto de apoio do teto são importantes para inverter o sentido de aplicação da força. Observa-se também a presença de roldanas móveis no sistema, que são úteis pelo fato de diminuírem a intensidade da força necessária para levantar as latas cheias de areia na parte inferior.

http://www.fis.unb.br/exper/prolego/geral/roldana.htm

http://www.definitions.net/definition/block and tackle
Block and tackle - A block and tackle is a type of compound pulley where several pulleys are mounted on each axle, further increasing the mechanical advantage. Block and tackles usually lift objects with a mechanical advantage greater than 2.
http://en.wikipedia.org/wiki/Pulley

O que sao cavalos vapor - cavalos de forca - [ Translate this page ]
Entretanto, basta consultar Como funciona o sistema de roldana, para perceber que as polias combinadas são capazes de conciliar facilmente peso percebido
http://webcache.googleusercontent.com/search?q=cache:IEA3Rxz...