Answer to Question #214026 in Classical Mechanics for Reece

Question

A rigid horizontal bar with weight 16 kN supports three parallel, vertical, straight wires with upper ends firmly secured. The weight of the bar causes the same elongation in each wire. Wire 1 has Area (A)= 20 mm^2 and is made of steel. Wire 2 has Area (A)= 40 mm^2 and is made of copper. Wire 3 is an alloy with Load= 40 kN, elongation of 30 mm over 3 m length. The length of each wire is 3 m. E(Steel)= 200 GPa, E(Copper)= 100 GPa and E(Alloy)= 120 GPa

Answer 1

$E_CA_C=F_Cl_C,$

$E_SA_S=F_Sl_S,$

$E_AA_A=F_Al_A,$

$f=\Sigma F\frac l2,$

$f=5.34~kN,$

$l=3.99~mm.$