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Math Help - Static Friction

  1. #1
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    Static Friction

    The machine part ABC is supported by a frictionless hinge at B and a 10degree wedge at C. Knowing that the coefficient of static friction is 0.20 at both surfaces of the wedge, determine (a) the force P required to move the wedge to the left (b) the component of the corresponding reaction at B. I've included a picture of the object to upload.

    So far I've got the moment about C or Mc=(-Byx10) + (-120x8) => By = -96 N
    and I'm lost on finding the normal force exerted on point C which is the key to the problem. : /
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  2. #2
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    Finding normal at C

    The chair (machine piece ABC) has a total weight of 120 lbs. Assuming a constant cross section, you can find the center of mass (lies along B & C, closer to B). The torque about the center of mass should be zero, this gives you the forces at B and C (since you already know the moment arms to B and C, and that the total force is 120lbs).
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  3. #3
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    But how would i find Bx? : /
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  4. #4
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    Components of a force

    Where the force P is applied, it separates into an x component and a y component because of the 10 degree angle of the block. That's the force pushing left. You have a force pushing right from friction and the force from the hinge. The force from friction is the normal force times the static coefficient of friction. What's left must be from the hinge.
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