Farrow's military encyclopedia : a dictionary of military knowledge . venient. The .single moradle pvlley,with parallel cords, gives a mechani-cal advantage = 2, for a little con-sideration will show that as thew-eight, W, is supported by the twostrings, the strain on each string isAW, and the strain on the one beingsupported by the hook, the power,P, requires merely to support thestrain on tin- other string. The fixedjjulley, is only of service in cliangingthe naturally upward direction ofthe power into a downw-ard the strings in tlie single movablepulley are not parallel, there is adi
Farrow's military encyclopedia : a dictionary of military knowledge . venient. The .single moradle pvlley,with parallel cords, gives a mechani-cal advantage = 2, for a little con-sideration will show that as thew-eight, W, is supported by the twostrings, the strain on each string isAW, and the strain on the one beingsupported by the hook, the power,P, requires merely to support thestrain on tin- other string. The fixedjjulley, is only of service in cliangingthe naturally upward direction ofthe power into a downw-ard the strings in tlie single movablepulley are not parallel, there is adiminution of mechanical advantage—/. (., P must he more than half ofWto produce onexiict counter|)oise ;if tlie auirle made liy the strings is120\ P must lie e(|ual to W; and ifthe angle be greater than this, thereis a great inecliaiiic:il disadvantage, or P must begreater than W. The following are examples of dif-ferent combinations of ])ulleys. nciicmlly known asthe tirst, second, and third systems of pulleys. Inthe first system, one end of each cord is fastened. 22 13 14 etc. 1. Steam winch. 2. Coinpouud pulleys. 3,12. Movable cranes. 4. Joints crane. 5. Hydi tootIhmI jack. 11. Jack-screw. 12, Movable double compound crane. 13. Compound pulley. 14. FulUXII-270.
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Keywords: ., bookcentury1800, bookdecade188, booksubjectmilitaryartandscience
