Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Complex pulley for a boat

  1. Jul 12, 2010 #1
    A guy at work gave me this drawing I have attached and asked me to find the pulley ratio. Do I need any other information such as rope lengths, pulley diameters, or load? I traded in my machine design book and don't remember exactly how to calculate the ratio. Is there anything else I can calculate involving the load that would be helpful if I knew the weight of the boat. Thanks for any info.

    Attached Files:

  2. jcsd
  3. Jul 12, 2010 #2


    User Avatar

    Staff: Mentor

    Nope, you don't need anything other than what is in the picture.
  4. Jul 13, 2010 #3
    So what I do is break up the pulley into sections and add up the tensions (T) right? With the tensions from each section I can get the ratio? Is this correct? I re-drew the drawing with my work on it. 9T:1T is my answer I just need someone to check that.

    Attached Files:

  5. Jul 19, 2010 #4
    Can anyone confirm my answer or is it off?
  6. Jul 19, 2010 #5


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Check to verify the sum of the forces is equal to zero in both the X and Y directions. Also verify the tension in any given rope is constant. If both of these are good, then the system is in static equilibrium.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook