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Homework Help: Equilibrium Problem

  1. Jun 9, 2010 #1
    1. The problem statement, all variables and given/known data
    Please see attachment.

    2. Relevant equations

    Summation F(x)=0

    Summation F(y)=0

    Summation tau=0

    3. The attempt at a solution
    Please see attachment.

    I know how to calculate the problem but I don't know the last part of the solution why the examinar choose mu(min)=1. Please help me.Thank you.

    Attached Files:

  2. jcsd
  3. Jun 10, 2010 #2


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    You have already seen that the force of friction is the same 4N at all points. That's what's required to keep the system at equilibrium. Imagine starting with a large μ and reducing it gradually. Slipping will occur at the point where the maximum value that static friction can have (=μ R) goes just below the value 4 N first. So if you write

    μR = 4 N,

    at which of the three points A, B and C μR falls below 4 N first as you make μ smaller?
  4. Jun 12, 2010 #3
    Thank you very much for explaination.Firstly I don't understand so I read many times your concept. Now I understand. I really appreciate you. Sorry for replying late.
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