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Homework Help: Work and Friction

  1. Dec 10, 2004 #1
    I am having real trouble understanding friction force. Work I understand. I just don't know how to put them together. Some help would be highly appreciated.

    A 16.1 kg block is dragged over a rough, horizontal surface by a constant force of 118 N acting at an angle of 25 degrees above the horizontal. The block is displaced 78.6 m, and the coeficient of kinetic friction is 0.228. The acceleration of gravity is 9.8 m/s2.

    a.) Find the work done by the 118 N force. Answer in units of J. - I've already found this to be 8405.82346 J

    b.) Find the work done by the force of friction. Answer in units of J.

    c.) If the block was originally at rest, determine its final speed. Answer in units of m/s2.
    Last edited: Dec 10, 2004
  2. jcsd
  3. Dec 10, 2004 #2
    Net work done on object = (horizontal component of 118 - frictional force) * distance

    Net work done on object = change in kinetic energy (work-energy theorem)
  4. Dec 10, 2004 #3


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    Please,review both the text (the first question and the second are identical),and the result to your first calculation.
    For the third,compute the time in which the body moves along those 78,6 m and from there,u can find the velocity.
  5. Dec 10, 2004 #4
    Alright. Fixed.
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