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!

Work Energy Question

  1. Sep 18, 2008 #1
    1. The problem statement, all variables and given/known data

    Uniform chain of length 'L' and mass of 'M' is lying on smooth table and one third of it's length is hanging vertically down over the edge of the table. If 'g' is acceleration due to gravity , then work required to pull the hanging part onto the table is :

    (I.I.T :- 1985)
    2. Relevant equations

    3. The attempt at a solution

    mass of hanging part will be m/3. so it will be exerting mg/3 force downward.
    so this amount of force is required to pull it up.when the chain will be up its displacement along table will be l/3 because now hanging part is on table.

    Work = F*S= Mgl/9

    But it is the wrong answer.
  2. jcsd
  3. Sep 18, 2008 #2


    User Avatar
    Homework Helper

    [tex]Work = \Delta PE =M*g*h = \frac{m}{3}*g*\frac{L}{2*3} = \frac{m*g*L}{18}[/tex]

    Your weight is MG/3 as you noted but the height that you raise the center of mass is 1/2 the length, which makes it L/6, not L/3.
  4. Sep 20, 2008 #3
    Thanks a ton!! You all are great . The site rocks.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Work Energy Question
  1. Energy/Work Questions? (Replies: 5)