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Book on table moved to Shelf

  1. May 20, 2009 #1
    1. The problem statement, all variables and given/known data
    A 1.7 kg book is lying on a 0.99-m-high table. You pick it up and place it on a bookshelf 2.43 m above the floor.
    How much work does gravity do on the book


    2. Relevant equations
    Wmg=mgYi-mgYf


    3. The attempt at a solution

    I thought that is the correct equation so I simply just plugged and chugged but it came out wrong. What did I do wrong?
     
  2. jcsd
  3. May 20, 2009 #2

    berkeman

    User Avatar

    Staff: Mentor


    It might just be a sign error. Note that the question asks for the work done by gravity on the book. But the postive work done is by the person lifting the book....
     
  4. May 20, 2009 #3
    Sorry guys I jumped the gun on this one. I soon realized that I just had to reverse my orginal equation. The equation that I have is for the work done by your hands picking the book up.
     
  5. May 20, 2009 #4
    I just posted as you posted yeah, thanks for the help!
     
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