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Homework Help: Uniform rod resting against rough vertical wall supported by a string.

  1. Apr 23, 2014 #1
    1. The problem statement, all variables and given/known data
    Uniform rod AB with end B resting against rough vertical wall. Coefficient of friction between wall and rod is μ.

    Rod is 2m long and has mass 3kg.

    Rod is kept in limiting equilibrium by a light inextensible string, one end of which is attached to the end A of the rod and the other to point C on the wall 2m above B. Angle ABC=120°.

    The end B of the rod is about to slip down the wall.

    1. By taking moments about C, show that the normal reaction at B is approx. 12.7N.

    2. Find the value of μ.

    PS: A labelled diagram would be very helpful! Thanks!

    2. Relevant equations

    3. The attempt at a solution

    Have been able to sketch what I think are all the forces acting on the rod, but does the normal reaction + friction + T-resolved = downward force of 2g-resolved? Do I take the weight of the rod to act from the centre?
    Last edited: Apr 23, 2014
  2. jcsd
  3. Apr 23, 2014 #2
    Yes, it would! Can you provide one?
  4. Apr 24, 2014 #3
    No worries.

    http://imageshack.com/a/img836/6874/gykt.png [Broken]
    Last edited by a moderator: May 6, 2017
  5. Apr 24, 2014 #4
    Yes, unless otherwise stated, its safe assume the rod is uniform in which case its center of gravity is at the center
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