The wires AB and AC are made of steel, and wire
AD is made of copper. Before the 150-lb force is applied,
AB and AC are each 60 in. long and AD is 40 in. long.
If the temperature is increased by 80_F, determine the
force in each wire needed to support the load. Take
E st = 29(10 3 ) ksi, E cu = 17(10 3 ) ksi, a st = 8(10 -6 )>_F,
a cu = 9.60(10 -6 )>_F. Each wire has a cross-sectional area
of 0.0123 in2.