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Homework Help: Physics lab; deriving for μs and μk

  1. Oct 30, 2012 #1
    1. Physics Lab :
    The problem statement, all variables and given/known data

    design, run and report an experiment to calculate A) μs B) μk between a flat bottomed object and a flat surface ( include a section called "theory" in which you formally derive an expression for μs and μk )

    im basically just having troubles deriving , i measured the angle in which my object has started to slide and its about 10 degrees

    2. relevant equations

    3. The attempt at a solution
    μs :

    Fun x = Sum x
    0 N = Fg x + Ffs
    0 N = mgcos(theta) -μsFN
    0 N = mgcos(theta) - μs(mgsin(theta))
    mgcos(theta)= μs(mgsin(theta))
    mgcos(theta) / mgsin(theta) = μs
    μs= cot(theta)

    im pretty sure im supposed to get μs= tan theta, any clue what i did wrong S:
    Last edited by a moderator: Oct 30, 2012
  2. jcsd
  3. Oct 31, 2012 #2
    Fgx is the sin theta component and FN the cosine component of Fg if theta is the angle that the flat surface makes with the floor.

    Attached Files:

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