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purchase
purchase, a mechanical device to increase force, whether by means of levers, gears, or blocks, or pulleys rove with a rope or chain. In its maritime meaning it is only the last of these which is known as a purchase: a rope rove through one or more blocks by which the pull exerted on the hauling part of the rope is increased according to the number of sheaves in the blocks over which it passes.
Where two or more blocks are involved in the purchase, it is generally known as a tackle, though there are exceptions to this general rule when two double or two treble blocks are used, these being known as twofold and threefold purchases respectively. The blocks of a tackle are known as the standing block and moving block, the rope rove through them is known as the fall and is divided into three parts known as the standing, running, and hauling parts. The amount by which the pull on the hauling part is multiplied by the sheaves in the blocks is known as the mechanical advantage. Twofold and threefold purchases are used only for heavy lifting, such as hoisting boats inboard. When rove to advantage, their theoretical mechanical gains are 5 and 7 respectively, when rove to disadvantage, the gains are 4 and 6, though in each case the loss due to friction of the sheaves is considerable since more sheaves are used. Allowing for average friction these gains are reduced to 3.57 and 4.37 when rove to advantage, and 2.26 and 3.75 when rove to disadvantage. See also gun tackle. |
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"purchase." The Oxford Companion to Ships and the Sea. 2006. Encyclopedia.com. 28 May. 2012 <http://www.encyclopedia.com>. "purchase." The Oxford Companion to Ships and the Sea. 2006. Encyclopedia.com. (May 28, 2012). http://www.encyclopedia.com/doc/1O225-purchase.html "purchase." The Oxford Companion to Ships and the Sea. 2006. Retrieved May 28, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O225-purchase.html |
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purchase
pur·chase / ˈpərchəs/ • v. [tr.] 1. acquire (something) by paying for it; buy: Mr. Gill spotted the manuscript at a local auction and purchased it for $1,500. ∎ archaic obtain or achieve with effort or suffering: the victory was purchased by the death of Rhiwallon. 2. Naut. haul in (a rope or cable) or haul up (an anchor) by means of a pulley, lever, etc. • n. 1. the action of buying something: the large number of videos currently available for purchase| we carefully make our purchases after consulting each other. ∎ a thing that has been bought: she stowed her purchases in the car. ∎ Law the acquisition of property by means other than inheritance. ∎ archaic the annual rent or return from land. 2. a hold or position on something for applying power advantageously, or the advantage gained by such application: the horse's hooves fought for purchase on the slippery pavement | [in sing.] an attempt to gain a purchase on the soft earth. ∎ a block and tackle. DERIVATIVES: pur·chas·a·ble adj. pur·chas·er n. |
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"purchase." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. 28 May. 2012 <http://www.encyclopedia.com>. "purchase." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. (May 28, 2012). http://www.encyclopedia.com/doc/1O999-purchase.html "purchase." The Oxford Pocket Dictionary of Current English. 2009. Retrieved May 28, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O999-purchase.html |
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purchase
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T. F. HOAD. "purchase." The Concise Oxford Dictionary of English Etymology. 1996. Encyclopedia.com. 28 May. 2012 <http://www.encyclopedia.com>. T. F. HOAD. "purchase." The Concise Oxford Dictionary of English Etymology. 1996. Encyclopedia.com. (May 28, 2012). http://www.encyclopedia.com/doc/1O27-purchase.html T. F. HOAD. "purchase." The Concise Oxford Dictionary of English Etymology. 1996. Retrieved May 28, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O27-purchase.html |
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Purchase
PURCHASETo buy; the transfer of property from one person to another by an agreement. Under theuniform commercial code(UCC), taking by sale, discount, negotiation, mortgage, pledge, lien, issue, reissue, gift, or any voluntary transaction. |
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"Purchase." West's Encyclopedia of American Law. 2005. Encyclopedia.com. 28 May. 2012 <http://www.encyclopedia.com>. "Purchase." West's Encyclopedia of American Law. 2005. Encyclopedia.com. (May 28, 2012). http://www.encyclopedia.com/doc/1G2-3437703599.html "Purchase." West's Encyclopedia of American Law. 2005. Retrieved May 28, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1G2-3437703599.html |
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purchase
purchase v. haul up (a rope, cable, or anchor) by means of a pulley or lever.
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"purchase." The Oxford Essential Dictionary of the U.S. Military. 2001. Encyclopedia.com. 28 May. 2012 <http://www.encyclopedia.com>. "purchase." The Oxford Essential Dictionary of the U.S. Military. 2001. Encyclopedia.com. (May 28, 2012). http://www.encyclopedia.com/doc/1O63-purchase.html "purchase." The Oxford Essential Dictionary of the U.S. Military. 2001. Retrieved May 28, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O63-purchase.html |
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purchase
purchase •abyss, amiss, bis, bliss, Chris, Diss, hiss, kiss, Majlis, miss, piss, reminisce, sis, Swiss, this, vis
•dais
•Powys, prowess
•loess, Lois
•Lewes, lewis
•abbess • ibis
•Anubis, pubis
•cannabis • arabis • duchess • purchase
•caddis, Gladys
•Candice
•Sardis, Tardis
•vendace • Charybdis
•bodice, goddess
•demigoddess • Aldiss • jaundice
•de profundis • prejudice • hendiadys
•cowardice • stewardess • preface
•Memphis • aphis • edifice • benefice
•orifice • artifice • office
•surface, surface-to-surface
•undersurface • haggis • aegis
•burgess
•clerkess, Theodorákis
•Colchis
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"purchase." Oxford Dictionary of Rhymes. 2007. Encyclopedia.com. 28 May. 2012 <http://www.encyclopedia.com>. "purchase." Oxford Dictionary of Rhymes. 2007. Encyclopedia.com. (May 28, 2012). http://www.encyclopedia.com/doc/1O233-purchase.html "purchase." Oxford Dictionary of Rhymes. 2007. Retrieved May 28, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O233-purchase.html |
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