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Finding acceleration using static/kinetic friction, mass & applied force?

  1. Jan 21, 2013 #1
    1. The problem statement, all variables and given/known data

    a fridge with a mass of 120kg is at rest on a kitchen floor. If Ms is 0.32 and Mk is 0.28 and you apply 472N of force what will be the acceleration of the fridge?

    m=120kg
    Ms=0.32
    Mk=0.28
    Fa=472N

    2. Relevant equations

    Ff=MFn

    Fw=mg
    Fw=1176N
    Fn=1176N

    F=ma


    3. The attempt at a solution

    not sure how to start solving for acceleration. was thinking that i needed to find the net force so that i could plug it into F=ma and solve for acceleration, but i am unsure how to find net force from the given information. could use the Ff=MFn equation but im not sure whether to plug in static or kinetic friction. any help is appreciated, thank you!
     
  2. jcsd
  3. Jan 22, 2013 #2

    CWatters

    User Avatar
    Science Advisor
    Homework Helper

    There are two steps to the problem...

    Is the applied force enough to overcome the static friction? If not the fridge won't move so acceleration = 0.

    If it is then your approach is correct. Use Mk in the equation.

    Basically as soon as it starts moving friction drops from Ms to Mk. So you can ignore Ms when working out the net force.
     
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