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Homework Help: Find work on raising a bucket on a rope

  1. Aug 25, 2007 #1
    1. The problem statement, all variables and given/known data
    An old oaken bucket of mass 7.25kg hangs in a well at the end of a rope. The rope passes over a frictionless pulley at the top of the well, and you pull horizontally on the end of the rope to raise the bucket slowly a distance of 6.00m.
    a.) How much work do you do on the bucket in pulling it up?
    b.) How much work is done by the gravitational force acting on the bucket?
    c.) What is the total work done in the bucket?

    2. Relevant equations
    W = Fscos(theta)
    3. The attempt at a solution
    a.) Work for bucket in pulling up:
    So total force done is Fw = (7.25kg)(9.8m/s^2)
    W = (7.25kg)(9.8m/s^2)(6.00m)
    W = 426.3N

    b.) Gravitational force :
    W = 426.3N

    c.) Total Work:
    Wgrav is only acting i think the total work is
    Wtotal = Wgrav
    Wtotal = 426.3N

    not sure
  2. jcsd
  3. Aug 25, 2007 #2


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    Homework Helper

    The units of work and energy are J (joules). So it should be 426.3J

    Other than the units, a) is right.

    b) should be -426.3J, because gravity is acting downwards, but the bucket is moving upwards... you've written gravitational "force"... did you mean gravitational work?

    c) total work = 0J,

    This is all assuming that the bucket starts and ends at rest... which I think is safe to assume for the problem.
  4. Aug 25, 2007 #3
    thanks alot learningphysics
    yep b is gravitational force but i ur ans is correct
    Last edited: Aug 25, 2007
  5. Aug 25, 2007 #4


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    Homework Helper

    you're welcome. :smile:
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