An arrangement for pulling a pipe out of the ground is shown in the figure. A cable ABC is attached to the pipe at A and to the sturdy frame at C. A second cable BDE is then clamped to the first cable at B and attached to the frame at E. Finally, a man pulls vertically downward on the second cable at D with a force Q. The lengths of the cab les are such that AB is vertical, BD is horizontal, BC is inclined by a small angle β to the vertical, and DE is inclined by a small angle f3 to the horizontal. The effective cross-sectional area of the cable is denoted Ac.
(a) Obtain a formula for the tensile stress σab in cable AB.
(b) Calculate the stress aab and also the lifting force P in cable AB for Q = 445 N, α = 5°, β = 8°, and Ac = 77 mm2.
