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!

Homework Help: Work done pulling up a curtain

  1. May 21, 2010 #1


    User Avatar

    1. The problem statement, all variables and given/known data

    A curtain is rolled up a thin rod. There is no friction. The length of the curtain is l=2m and weight is m=2kg. Find the work done.

    EDIT: the mass is 1kg not 2.

    2. Relevant equations


    3. The attempt at a solution
    The solution is A=9.81J The way I did it was that the work done is the area under the curve on the F/s plot. Since the force needed to pull drops linearly, I simply multiplied mg*l and then I divided that by two. Is this approach valid? The answer is correct.
    Last edited: May 21, 2010
  2. jcsd
  3. May 21, 2010 #2
    mg*L/2 equals 19.6 J are you saying that 9.81 J is supposed to be the correct answer? I assumed that the center of mass of the curtain was at L= 1 m and that mass was lifted 1 meter to the top of the window. Work = Force * distance * Cos(0)
  4. May 21, 2010 #3


    User Avatar

    I mistyped the mass, it is 1kg.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook