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Homework Help: What is the coefficient of friction between surface and the mass?

  1. Feb 23, 2010 #1
    1. The problem statement, all variables and given/known data
    A mass of 50 kg is kept in uniform motion along a horizontal surface by a horizontal force of 4.08x10^6 dynes. What is the coefficient of friction between surface and the mass?

    2. Relevant equations
    (I searched previous answered questions and found this)
    Ff= u * mg

    3. The attempt at a solution
    Our teacher hasn't actually started with our friction topic yet, but she always makes us do these assignments beforehand so we come "prepared" to her lectures. But I have no idea how to start. So I tried this, but I think it's incorrect.

    4.08 x 10 ^ 6 dyn / (50 kg * 9.8 m/s^2) = 8326.531

    Coefficients aren't supposed to be that big, right? So I tried converting. This is really embarrassing, but I'm not familiar with dyn so I had to look for its conversion factor to meters.

    40.8 m / (50000 g * 9.8 m/s^2) = 8.32 x 10 ^-5

    Even just clearing out the dyn thing would be great. I mean, if the values I used are correct? :) Thanks.
  2. jcsd
  3. Feb 23, 2010 #2


    User Avatar
    Homework Helper

    Hi yss83, welcome to PF.
    Convert dyne to newton.
    Keep mass in kg, and g in m/s^2.
    Now find u.
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