Wize University Statics Textbook (Master) > Equilibrium of a Particle

PROCEDURE:     SAME AS FOR 2D  >   Sum F's = 0  (in x, y, and z (if 3D))

HELPFUL HINTS:  IF 3D Geometry is difficult > 
express each FORCE in Cartesian Vector Form (i, j, k)
substitute these vectors into SUM F = 0
set i, j, k components = 0
BE CAREFUL TO CHECK AXES orientation before writing vectors in CVF !!!!!!!!   

Determine the magnitudes of F1, F2, and F3 for equilibrium of the particle.

1) write each vector in CV Form:

F1 = F1cos60°i + F1cos135°j + F1cos60°

F2 = F1i

F3 = -F3j

F200 = -200k

F800 = -800(3/5)i + 800(4/5)j
          = -480i + 640j

2) equilibrium requires that sum x's=0, sum y's=0, and sum z's=0

x:   F1cos60° + F1 -480 = 0
y:   F1cos135° -F3 + 640 = 0
z:   F1cos60° - 200  = 0

3) solve for each:
     F1=400 lb
     F2=280 lb
     F3=357 lb   

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Determine the force in each cable if F = 500 lb.

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