Editing Pulley (section)

==Block and tackle==
[[Image:Tackles.png|thumb|360px|right|Various ways of rigging a tackle<ref name="advantage" />]]
A block is a set of pulleys (wheels) assembled so that each pulley rotates independently from every other pulley. Two blocks with a rope attached to one of the blocks and threaded through the two sets of pulleys form a [[block and tackle]].<ref>{{cite web
  |last = Prater         |first = Edward L. 
  |title = Basic Machines
  |publisher = Naval Education and Training Professional Development and Technology Center, NAVEDTRA 14037           |date = 1994
  |url = http://www.constructionknowledge.net/public_domain_documents/Div_1_General/Basic_Skills/Basic%20Machines%20NAVEDTRA%2014037%201994.pdf
}}</ref>
<ref>{{cite book
 |author       = Bureau of Naval Personnel
 |title        = Basic Machines and How They Work
 |publisher    = Dover Publications
 |date         = 1971
 |orig-year    = 1965
 |url          = http://www.webpal.org/SAFE/aaarecovery/5_simple_technology/basic_machines.pdf
 |isbn         = 0-486-21709-4
 |access-date  = 2011-12-13
 |archive-url  = https://web.archive.org/web/20160922221747/http://www.webpal.org/SAFE/aaarecovery/5_simple_technology/basic_machines.pdf
 |archive-date = 2016-09-22
 |url-status   = dead
}}</ref>

A [[block and tackle]] is assembled so one block is attached to the fixed mounting point and the other is attached to the moving load. The [[ideal mechanical advantage]] of the block and tackle is equal to the number of sections of the rope that support the moving block.

In the diagram on the right, the ideal mechanical advantage of each of the block and tackle assemblies<ref name="advantage">{{cite book |title=Handbook of Rigging: For Construction and Industrial Operations |url=https://books.google.com/books?id=Q86UKqYui-0C |publisher=McGraw-Hill Professional |isbn=978-0-07-149301-7 |last=MacDonald |first=Joseph A |date = 14 June 2008|pages=376}}</ref> shown is as follows:
* Gun tackle: 2
* Luff tackle: 3
* Double tackle: 4
* Gyn tackle: 5
* Threefold purchase: 6