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Homework Help: Block and Tackle System

  1. May 30, 2006 #1
    Given a block and tackle system and a known weigt, give the magnitude of the forces at the numbered points. [see attached for figure]
    https://www.physicsforums.com/attachment.php?attachmentid=7026&stc=1&d=1149034106
    blocktackle.JPG

    My answers:
    Point 2: 20
    Point 3: 20
    Point 4: 10
    Point 1: 40

    I arrived at the answers simply by looking at the figure and do a force balance at each tackle. I think some (if not all) are wrong because the systems doesn't provide any mechanical advantage (according to my answers). Please Help.
     

    Attached Files:

  2. jcsd
  3. May 30, 2006 #2

    Doc Al

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    Staff: Mentor

    Looks OK to me (assuming all ropes are essentially vertical). Why do you say there's no mechanical advantage? A 10 unit weight (shown) lifts a 20 unit weight (that's point 2).
     
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