Load PA is acting at A, and load PB is acting at B of horizontal link 3. Link 3 is pinned to vertical link 2 at O, and link 2 is fixed in ground link 1 at D. The lengths are AO = 4 ft, OB = 2 ft, and DO = 6 ft. Both links have solid circular cross Figure P11.42 Link AB supporting two loads.

sections with diameter D = 2 in and are made from a steel alloy with compressive yield strength Syc = 85 000 psi, tensile yield strength Syt =

75 000 psi, and modulus of elasticity E = 30 ×

106psi. Assuming that links 2 and 3 are in static equilibrium and using the theoretic value for the end-condition constant for link 2, determine: (a)

the magnitude of force PB that is acting as shown at B if PA = 30 000 lb;

(b) the critical load, the critical unit load, and the factor of safety to guard against buckling for link 2; and

(c) the diameter of a solid circular cross section for link 2 that will ensure the factor of safety guarding against buckling of the link is N = 4.