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Statics, Springs and Friction

  1. Nov 24, 2012 #1
    1. The problem statement, all variables and given/known data

    The unstretched length of a spring is 1.5 ft. What friction coefficient,μ, at A and C is needed so that P=500 lb would tend towards points A and C sliding outward? Given spring constant k=70 lb/ft

    Inverted triangle such that height is 4 ft to point B. Force P points directly down at the tip of triangle (point B). Width at base between points A and C is also 4 ft. Spring is located 1 ft off horizontal between two legs of triangle.

    2. Relevant equations

    Friction=μ*Normal force

    F(spring)=kΔx=(70 lb/ft)Δx

    3. The attempt at a solution

    I drew a free body diagram of half the system showing the P=500 lb downward, the spring force, the friction force and the normal force. Summing the forces in the y, I came to the Normal force equal to 500 lb. Then summing the forces in the x you have the friction force equal to the spring force. Here is where I get stuck. If you are trying to find μ what should the value of Δx be such that the system would tend towards sliding outward?
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
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