1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Pulley Hoist Free Body Diagram

  1. Mar 5, 2013 #1
    Hi All,

    I am an old dog, and rusty propeller head. I am having the most difficult time figuring out the forces on a pulley system I am working on. Can someone please review my sketch and tell me if I am even close. I would accept any suggestions and direction.

    Much Obliged

    Attached Files:

  2. jcsd
  3. Mar 5, 2013 #2


    User Avatar
    2017 Award

    Staff: Mentor

    How can you support W/2 with two strings of W/8 tension (in addition, they have some angle between them!)
    In addition, what happens to the end of the string (right side)? I think it should help to support the weight, too.

    W/8 is a force, the tangent of a force is not well-defined.
  4. Mar 5, 2013 #3
    Yes, I knew my W/2 did not add up correctly with 2 - W/8 loads. That is really where I need help.

    W = Load
    W/2 is a pulley at each end of the W
    The angle is not counted at this time to avoid further confusion.
    The end of the string is lifting W
    I drew the tangent of middle pulleys for reference. The load on them will not affect my system I am building. I can calculate the load after I correctly figure out the force multiplier of my pulleys.

    I hope I helped clear some up your questions.
  5. Mar 5, 2013 #4


    User Avatar
    2017 Award

    Staff: Mentor

    The end of the string is lifting the same as all other parts. If we approximate that those string elements are vertical, we have 5 times the string tension holding that weight W, so string tension is W/5.
  6. Mar 5, 2013 #5
    Thank you,

    So that I have more understanding...

    Is the weight only carried by the string between pulleys B-C, C-D, G-H, H-I , I-to end?

    Also; Is my W/2 at pulleys C and H correct?

    Do I substitute W/5 for where I have W/8 throughout the string?

  7. Mar 6, 2013 #6


    User Avatar
    2017 Award

    Staff: Mentor

    As the other parts are not connected to the weight... sure.
    No, as you did not consider the end here.
  8. Mar 6, 2013 #7
    Thank you !

    I believe I have all that I need.

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Pulley Hoist Free Body Diagram
  1. Free Body Diagram (Replies: 1)