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Finding the Angle When the Crate Begins to Slip

  1. May 25, 2017 #1
    1. The problem statement, all variables and given/known data
    A crate is placed on an adjustable, inclined board. The coefficient of static friction between the crate and the board is 0.29. A) Calculate the angle at which the crate just begins to slip.

    2. Relevant equations
    Sum of Forces=M*A

    3. The attempt at a solution
    In my problem: Why is g cancelled? and why is 0.29 added to tan^-1
    These are highlighted areas

    Attached Files:

  2. jcsd
  3. May 25, 2017 #2


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    Your picture is so tiny it is not readable
  4. May 25, 2017 #3
    Hmm weird.. I can see it clearly even from my phone. Its my first post maybe I messed something up.
  5. May 25, 2017 #4
    Weird.. I can see it from my phone clearly. Maybe I did something wrong
  6. May 25, 2017 #5


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    so it looks like you have in the one section: = 0 < g*(sinθ - μ*cosθ). Just multiply both sides by 1/g and you have 0/g < (g/g)*(sinθ - μ*cosθ). 0/g is 0, and g/g is 1.
    For the last part, they get it down to μ < tanθ, then plug in μ=0.29 which is given in the problem statement. Take inverse tangent of both sides to find θ.
  7. May 25, 2017 #6
    When I was young, I had excellent near vision. Now . . . not so much. However, even when I downloaded the photo and zoomed in, I can still see well enough to realize there is a shortage of pixels; it is still very difficult to read. "And things that are too hard just aren't worth doing," said someone.

    Welcome to Physics Forums.
  8. May 25, 2017 #7


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    Strange.. if I click on the link it takes me to https://www.physicsforums.com/attachments/img_20170525_213308-jpg.204257/, an image that is quite readable even with my so-so vision. (But it is so misaligned to the frame that the top right corner is missing.)
    Anyway, scottdave has posted the answers to the OP questions.
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