Information AboutPulley |
| CATEGORIES ABOUT PULLEY | |
| mechanics | |
| simple machines | |
|
s.]] A pulley (also called a sheave) is a Wheel with a Groove along its edge for holding a Rope or Cable or Belt . 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. ROPE AND PULLEY SYSTEMS Rope and pulley systems (the rope may be a very strong cable) are characterized by the use of a single rope transmitting a linear motive force (in tension) to a load through one or more pulleys for the purpose of pulling the load (often against gravity.) They are often included in the list of Simple Machine s. In a system of ropes and pulleys, the mechanical advantage gained is ideally the number of pulleys in the system (or one less as a pulley is often used only to change the direction of the load). The tension in the rope is reduced by the mechanical advantage, while the distance (ie. the length of rope) is increased by the same proportion. Since a slender cable is more easily managed than a fat one (albeit shorter and stronger), pulley systems are often the preferred method of applying mechanical advantage to the pulling force of a Winch (as can be found in a lift Crane ). In practise, the more pulleys there are, the less efficient a system is. This is due to Friction in the system where cable meets pulley and in the rotational mechanism of each pulley. It is not recorded when or by whom the pulley was first developed. It is believed however that Archimedes developed the first documented Block And Tackle pulley system, as recorded by Plutarch . Plutarch reported that Archimedes moved an entire warship, laden with men, using compound pulleys and his own strength. Types of Systems
How it Works |
|
|