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Finding Applied Force from Coefficient of Friciton and mass

  1. Sep 6, 2013 #1
    So I've been stuck on this type of question, please help!!

    You are pushing horizontally on a 3.0 kg box of wood, pressing against a wall. If the coefficient of static friction is 0.60, how much force must you exert on the block to prevent it from sliding down?

    1. The problem statement, all variables and given/known data
    What is the force applied to keep the box from sliding down?

    m= 3.0kg
    u= o.60

    2. Relevant equations

    Fnet = ma

    3. The attempt at a solution

    I tried to use the equation FF=uFn:

    FF = .6(3)(9.81)
    FF=17.658 N

    Am I doing this correct?
  2. jcsd
  3. Sep 6, 2013 #2


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    Staff: Mentor

    Hi jmcpherson82. http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif [Broken]

    The vertical forces must balance. The upward force due to friction = 0.6 Fn
    Last edited by a moderator: May 6, 2017
  4. Sep 6, 2013 #3
    So how would I find Fnet without acceleration? Because then I can't do the equation Fnet = ma
  5. Sep 6, 2013 #4
    EDIT: Oh, N.O.'s talking about normal force not net force.
  6. Sep 6, 2013 #5


    User Avatar

    Staff: Mentor

    The upward force = the downward force

    The upward force is due to friction.
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