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Minimum coefficient of static friction

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  1. Nov 21, 2016 #1
    1. The problem statement, all variables and given/known data
    If the incline of the driveway is 19 ∘ from the horizontal, what must the minimum coefficient of static friction be between your shoes and the ice?

    2. Relevant equations
    Fs=uN

    3. The attempt at a solution
    IMG_7745.JPG
     
  2. jcsd
  3. Nov 21, 2016 #2
    i need help figuring out my error, i assumed that the N force was equal to mgcosθ and Fs was equal to mgsinθ. the masses must cancel out and following what is written on my paper, i got and answer of 0.15. this is incorrect and i need help finding out why
     
  4. Nov 21, 2016 #3

    haruspex

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    Degrees versus radians.
     
  5. Nov 21, 2016 #4
    i don't understand?
     
  6. Nov 21, 2016 #5

    haruspex

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    Did you plug the 19 degrees into the tan function of a calculator? It can probably be set to expect angles to be specified in degrees or radians, but you have to make sure you select the right one.
     
  7. Nov 21, 2016 #6
     
  8. Nov 21, 2016 #7
    so my original answer was in my radians and i did 9.8 tan (19) in degrees and got 3.4 as the answer, is that to big?
     
  9. Nov 21, 2016 #8

    haruspex

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    Why the 9.8? g is not part of the coefficient.
     
  10. Nov 21, 2016 #9
    well actually i know its incorrect
     
  11. Nov 21, 2016 #10
    so just tan (19)
     
  12. Nov 21, 2016 #11

    haruspex

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    Yes.
     
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