A copper wire is stretched with a stress of 60 MPa at 20˚C. If the length is held constant, to what temperature must the wire be heated to reduce the stress to 5 MPa? The value of αl for copper is 17.0 × 10-6 (°C)-1, the modulus of elasticity is equal to 110 GPa.

Respuesta :

Answer:

[tex]49.4^{\circ}[/tex]

Explanation:

We are given that

Stress,[tex]\sigma_1=60 MPa=60\times 10^6 Pa[/tex]

Temperature,[tex]T_0=20^{\circ}[/tex]

Stress,[tex]\sigma_2=5MPa=5\times 10^6 Pa[/tex]

[tex]\alpha=17\times 10^{-6}/^{\circ}C[/tex]

Modulus of elasticity=[tex]E=110GPa=110\times 10^9 Pa[/tex]

We have to find the temperature must the wire be heated.

[tex]T=T_0-\frac{\Delta\sigma}{E\alpha}[/tex]

Using the formula

[tex]T=20-\frac{(5-60)\times 10^6}{110\times 10^9\times 17\times 10^{-6}}[/tex]

[tex]T=49.4^{\circ}[/tex]