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^{ -6}m/m°C, Young's modulus 210 × 10

^{9}N/m

^{2}and yield stress 250 mega Pascal. With 100 meters length and 0.1 m

^{2}section area , If we increase its temperature 10 °C, how much energy will be produced by expansion force in Joules?

with young's modulus the answer is:

E= 12 × 10

^{-6}× 100 m × 10 °C × 210 × 10

^{9}× 0.1 m = 252 × 10

^{6}Joules

with yield stress the answer is :

E= 12 × 10

^{ -6}× 100 m × 10 °C × 250 × 10

^{6}× 0.1 m = 0.3 × 10

^{ 6}Joules

I have been confused that which one could be right?