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4-9 Force/mass - Newton's Second Law question

  1. Sep 15, 2009 #1
    1. The problem statement, all variables and given/known data

    When a horizontal force F is applied to a box having a mass m, the box sides on a level floor, opposed by a force of kinetic friction f.

    a. What magnitude of acceleration occurs for the box?
    b. Calculate the acceleration if the horizontal force is 412N, friction is 122N, and the mass of the box is 75kg

    2. Relevant equations

    It's asking for acceleration, so I am choosing a=Fnet/m for the formula. Now, the problem has a force and friction

    F - horizontal force 412N
    m - mass 75kg
    f - kinetic friction 122N
    a - ?


    3. The attempt at a solution

    a = 412N - 122N/75 kg
    a = 290N/75 kg
    a=3.86 I'm rounding the answer because it's close to four, so a is 4. Is this correct?
  2. jcsd
  3. Sep 15, 2009 #2
    well rounding because something is "close" is never correct how many sig. figs. do you have?
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