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Find the mass of object knowing the applied force and coefficient of friction

  1. Dec 6, 2008 #1
    1. The problem statement, all variables and given/known data

    If a force of 45 newtons is needed to overcome friction and the coefficient of friction=0.26, what is the mass of the object?

    3. The attempt at a solution

    So would I need to find the frictional force first? But then I can't use the equation: (frictional force=coefficient of friction x weight) since I dont have the mass. I also thought about using the equation F=MA but then I dont have the acceleration, the friction, or the net force! Any help, I'm really stuck?
     
  2. jcsd
  3. Dec 6, 2008 #2

    Doc Al

    User Avatar

    Staff: Mentor

    They give you the friction force. The way to interpret the given information is that the 45 N force is just enough to overcome friction, thus that force equals the friction.
    Sure you can use that equation. Remember that you're asked to find the mass.
     
  4. Dec 6, 2008 #3
    Ok, so what you're saying is that the applied force equals the friction, in this case. I thought it wouldn't move though if that was true? I'm just confused on this concept.

    But anyway, using that information, frictional force=coefficient of friction x weight
    45=0.26m(9.8)
    45=2.55m
    m=17.65kg
    Is that right?
     
  5. Jul 20, 2010 #4
    Yes.
    You are given two values, and you need to solve for one of them using an equation with four variables, three of which are known (the other being g).
     
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