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Homework Help: Coeficcient of Friction

  1. Mar 5, 2012 #1
    1. The problem statement, all variables and given/known data
    So I have and inclined plane at 1 degrees, and on top of it, there is an object 361grams. I gradually increase the angle of the inclined plane, and just at 20 degrees, the object starts to slide down. How do I find out the coefficient of friction?

    Any help would be appreciated.


    2. Relevant equations

    3. The attempt at a solution

    I only know that just before it is about to slide down, mgsin20-Ffmax=0
    so do i use 19.99999 degrees to solve this equation? So i used mgsin19.999=Usmgcos19.9999

    and got 1.299999N but I think its wrong.
  2. jcsd
  3. Mar 5, 2012 #2
    Not necessarily when resultant force is 0, the object does not move.

    For example, take the case when you are pushing an object with a force [itex]F[/itex], and there is a friction [itex]f[/itex] equal to the force you are applying, the object moves with constant speed [itex]v[/itex], but there is no acceleration. [itex]a = 0[/itex].

    [itex]F[/itex]resultant[itex] = m*a[/itex], so when [itex]F[/itex]resultant[itex] = 0[/itex] then you don't have acceleration.

    So basically, you don't have to make it 19.9999999, it is 20 degrees.

    I have attached a jpeg with the sketched problem. Have a look at it. Good luck
    Last edited: Jun 16, 2012
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