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Work done on a bucket

  1. Aug 28, 2016 #1
    1. The problem statement, all variables and given/known data
    An old oaken bucket of mass 6.75 kg 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 4.00m.
    A). How much work do you do on the bucket in pulling it up?



    2. Relevant equations
    ##W = FS##
    ##W = ΔKE##
    ##ΣFy = T - mg##


    3. The attempt at a solution
    First, I assumed the problem was implying that the bucket was in equilibrium when it said it was moving slowly. So since the weight is ##(9.81)(6.75) = 66.21 N##, the tension force must be equal to that.

    So, ##W = FS##. ##W = (66.21)(4) = 264.84 J##. This seemed like the correct answer to me, but when I look at the back of the book, it says the answer is 3.60 J.

    Where did I go wrong here? Thanks!
     
  2. jcsd
  3. Aug 28, 2016 #2

    Doc Al

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    Staff: Mentor

    I'd say your answer is correct. What book/problem is this from?
     
  4. Aug 28, 2016 #3
    That's what I thought too. It's from "Sears and zemansky's University Physics With Modern Physics, 12th edition".

    I guess there was a mistake or something in the answer key.
     
  5. Aug 28, 2016 #4

    Doc Al

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    Staff: Mentor

    Yep.
     
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