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Work Done by Gravity

  1. Dec 1, 2009 #1
    1. The problem statement, all variables and given/known data
    The problem asks, "You lift a 10N book up in the air a distance of 1m at a constant velocity of 0.5m/s. The work done by gravity is:

    a. -10J
    b.-5J
    c. zero
    d. 5J
    e. 10J


    2. Relevant equations
    W=FD
    Wg=mgh


    3. The attempt at a solution
    So, the work done by whoever is lifting the book is 10J (W=FD) but with the hand still holding the book, is gravity doing work? I just really can't decide if gravity is doing "work" in this situation. Can someone point me in the right direction? Thank you!
     
  2. jcsd
  3. Dec 1, 2009 #2

    fluidistic

    User Avatar
    Gold Member

    The definition of work involves a distance as you pointed out. If the book is on the ground, does the gravity do work? As it is not moving, no.
    By the way the definition of work can be found there : https://www.physicsforums.com/library.php?do=view_item&itemid=75. It's a line integral.
     
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