A Brass Wire (D = 2 $19.5 \times 10^{-6} /{ }^{\circ} \mathrm{C}$

Multiple Choice

A brass wire (d = 2.0 mm, E = 110 GPa) is pretensioned to T = 85 N. The coefficient of thermal expan- sion for the wire is $19.5 \times 10^{-6} /{ }^{\circ} \mathrm{C}$ . The temperature change at which the wire goes slack is approximately:

A) $+ 5.7 ^ { \circ } \mathrm { C }$
B) $- 12.6 ^ { \circ } \mathrm { C }$
C) $+ 12.6 ^ { \circ } \mathrm { C }$
D) $- 18.2 ^ { \circ } \mathrm { C }$