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Homework Help: Minimum Force to Make an Object Move

  1. Sep 19, 2010 #1
    1. The problem statement, all variables and given/known data
    A 6 kg object sits on a horizontal surface with coefficient of friction = .8. What is the minimum force (not necessarily horizontal) necessary to make the object slide?

    2. Relevant equations
    Fsmax = u * Fn
    where Fsmax is the force that must be overcome to make an object move, u is the coefficient of friction, and Fn is the normal force.

    3. The attempt at a solution
    I was just wondering if this seemed correct:
    Fg = -58.8 N (mass * g) so
    Fn = 58.8 N
    I'm not clear on when exactly one can make the assumption that Fg = Fn
    but then using that value of Fn I calculated Fsmax, so the minimum force necessary to make the block move is any force greater than Fsmax.
     
  2. jcsd
  3. Sep 19, 2010 #2
    You need to overcome the force of friction.

    The force of friction is
    Ff=(coefficent of friction)(weight of object in Newtons)
    Ff=(.8)(6*9.81)
    Ff=(.8)(58.86)
    Ff=47.088N

    I think :D
     
  4. Sep 19, 2010 #3

    cepheid

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    Staff Emeritus
    Science Advisor
    Gold Member

    One can always make the assumption that, if the acceleration in some coordinate direction is zero, then by Newton's second law, the sum of all forces acting along that direction must be zero.

    This condition for static equilibrium is the foundation for all introductory statics problems.
     
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