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Homework Help: Simple work problem

  1. Oct 18, 2007 #1
    Hello :)
    I must have missed something. This problem is extremely simple and yet I can't figure out what I'm doing wrong. Really frustrating!

    The problem:
    A 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 m.

    How much work do you do on the bucket in pulling it up?

    My Guess
    Since you need to raise the bucket, you need to pull with a force that equals the downwards gravitational force on the bucket. This is 6.75*9.8 = 66.15 N.
    Now you pull it a distance of 4 m. This is 66.15*4 = 264.6 J.

    But this is wrong! It's supposed to be 3.6 J

    What am I supposed to do, and more importantly, why is what I'm doing wrong? This is supposed to be so simple >.<
  2. jcsd
  3. Oct 18, 2007 #2

    Doc Al

    User Avatar

    Staff: Mentor

    It is simple and you're doing it correctly. That 3.6 J answer is bogus.
  4. Oct 18, 2007 #3
    You have solved the problem correctly. 3.6 J is incorrect.
  5. Oct 18, 2007 #4
    I sure hope you're both right. Thanks!
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