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Homework Help: Work problem

  1. Feb 24, 2008 #1
    1. The problem statement, all variables and given/known data
    A crate of mass 10.6 kg is pulled up a rough incline with an initial speed of 1.48 m/s. The pulling force is 104 N parallel to the incline, which makes an angle of 20.1° with the horizontal. The coefficient of kinetic friction is 0.400, and the crate is pulled 5.05 m.

    (a) How much work is done by the gravitational force on the crate?
    (b) Determine the increase in internal energy of the crate-incline system due friction.

    3. The attempt at a solution

    I have solved part A, and I got -180 J. I need help on B. I really don't know what the question is looking for. Thanks
  2. jcsd
  3. Feb 25, 2008 #2
    Increase in internal energy is decrease in kinetic energy.
  4. Feb 25, 2008 #3
    It may be easier to think about it in terms of the definition of work done by a force. That is,

    [tex]W = \int Fds[/tex]

    where the work done by friction rubs the molecules beneath the crate and heats it up, hence an increase in internal energy.
  5. Feb 25, 2008 #4
    So do I need to find the Work that is done by friction?
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