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Homework Help: The value of the friction force

  1. Mar 19, 2010 #1
    1. The problem statement, all variables and given/known data
    The worker pushes downward and to the left on the box at an angle of 35°. The box has a mass of 135 kg. The box moves horizontally across the floor to the left at a constant velocity. The force applied by the man is 2030 N∠215°. What is the value of the friction force?


    2. Relevant equations
    Fgravity · sin35° = Fgravityx
    Ffriction + Fgravityx = m · a
    f = μ · Fs


    3. The attempt at a solution
    sin35° =
    Fgravity · sin35° = Fgravityx
    m · g · sin35° = Fgravityx
    (135 kg)(9.81) sin35° = Fgravityx
    759.6 N = Fgravityx

    Ffriction + (759.6 N) = (135 kg)(0 m/s2)
    Ffriction - 759.6 N = 0 N
    Ffriction = 759.6 N

    I know that this isn't correct, because my study guide is multiple choice. My options are:
    a. 1164 N
    b. 1324 N
    c. 1663 N
    d. 2489 N

    I'm really not sure what I'm missing or if I am going the wrong way with finding the value of the friction force. My guess is that c. 1663 N is correct, but that is only a guess. I'd like to be able to prove which answer it is. Thank you for any help!
     
  2. jcsd
  3. Mar 19, 2010 #2

    rl.bhat

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    Homework Helper

    The worker pushes downward and to the left on the box at an angle of 35°
    The force applied by the man is 2030 N∠215°

    Can you explain what are these two angles? Whether the worker and the man are the same person?
     
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