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Acceleration and coefficients of friction

  1. Dec 12, 2011 #1
    how would you find the rate of acceleration when given the force, mass, and the coefficient of friction?? what would the formula(s) be??

    i am so confused! HELP!
     
  2. jcsd
  3. Dec 12, 2011 #2
    You'll need to give some more information about your problem, taking a stab at it I'll assume you have a block of mass [itex]m[/itex] sitting on a surface with coefficient of kinetic friction [itex]\mu[/itex] and there is a force [itex] F [/itex] acting on the block parallel to the surface it rests on.
    In that case the force of friction becomes
    [tex] F_{friction} = mg\mu [/tex]
    With [itex]g[/itex] being the acceleration due to gravity. Then from Newton's second law
    [tex] F_{net} = F_{friction} - F [/tex]
    The minus sign is because friction will act in the opposite direction to the motion of the block. From this you know that
    [tex]Acceleration_{net} = \frac{F_{friction} - F}{m} [/tex]
     
  4. Dec 12, 2011 #3
    Force = Mass x Acceleration

    You already have the force and the mass, the math is very easy to find the acceleration.

    Friction complicated it just a little, as friction is a force acting opposite of the direction of acceleration. So the "Force" in the above formula is actually "Force - Friction". As JHamm explained, the formula for "Friction" is probably Friction = Mass x 9.81 x coefficient of friction.

    Basically the exact same thing as JHamm said, but hopefully if two people say it, it will make more sense...
     
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