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Homework Help: Simple block kinematics problem

  1. May 16, 2012 #1
    1. The problem statement, all variables and given/known data

    Block A weighs 75lbf and the coefficients of static and kinematic friction between A and the plane are both 0.50. Determine the acceleration of A under the action of the 25 lbf force when the velocity at A is (a) 8fps up the plane, (b) 15 fps down the plane. (c) Zero.

    2. Relevant equations

    Sum of all forces = mass * acceleration

    3. The attempt at a solution

    I dont know where to start... the box is doing up a plane and it's cosine is 4/5 and its sine is 3/5.
     
  2. jcsd
  3. May 16, 2012 #2

    HallsofIvy

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    Science Advisor

    "Its cosine is 4/5 and its sine is 3/5". What is "its"?? Yes, I understand it is an angle but with the horizontal or vertical?
     
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