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Equilibrium giving me some trouble

  1. Apr 6, 2004 #1
    I just got done doing about 20 other problems but I can't figure this one out....

    A uniform plank, with a length L of 7.63 m and a weight of 420 N, rests on the ground and against a frictionless roller at the top of a wall of height h = 5.21 m. The plank remains in equilibrium for any value of q= 70° or more, but slips if q < 70. Find the coefficient of static friction between the plank and the ground.

    Any help would be appreciated
  2. jcsd
  3. Apr 6, 2004 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Start by identifying all the forces acting on the plank. Draw a diagram.

    Then realize that the plank is in equilibrium, so:
    ∑Fx = 0
    ∑Fy = 0
    ∑Torques = 0 (about any point)
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