1. Not finding help here? Sign up for a free 30min 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 Efficiency Problem (How much rope must be pulled)?

  1. Jan 12, 2012 #1
    1. The problem statement, all variables and given/known data
    A pulley system has an efficiency of 71.5 percent. How much of the rope must be pulled in if a force of 641 N is needed to lift a 160 kg desk 2.51 meters?


    2. Relevant equations

    IMA = De/Dr
    MA = Fr/Fe
    Efficiency (%) = Wo/Wi
    Efficiency (%) = MA/IMA

    I have absolutely no idea how to solve this; this is simply a practice problem that I made up and the professor said a similar problem will appear on the test. Could someone show me how to do this?? I would appreciate it greatly.


    3. The attempt at a solution
     
  2. jcsd
  3. Jan 13, 2012 #2

    SammyS

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    How much work is needed to lift the desk?

    Only 71.5% of the work done to the rope goes into lifting the desk.

    How much work needs to be does to the rope?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Pulley Efficiency Problem (How much rope must be pulled)?
Loading...