Calculating Elastic Energy: Where Did I Go Wrong?

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The user attempted to calculate elastic energy using the formula E=σε/2, substituting values for strain and stress. Their calculations led to an energy result of 880,000 J, which is significantly higher than the correct answer of 35.2 J. Key mistakes included incorrect unit conversions and misunderstanding that the calculation yielded energy per unit volume rather than total energy. Participants emphasized the importance of checking units and clarifying the context of the calculations. Accurate unit management is crucial for correct energy calculations in elastic materials.
Clara Chung
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Homework Statement


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Homework Equations

The Attempt at a Solution


I tried to use the equation introduced in the class, E=σε/2
ε=αΔT =2*10-5*200 = 4*10-3
and by σ=Yε, I get σ=110*109*4*10-3 = 4.4*109
so E=(4*10-3) * (4.4*109 ) /2 = 880000J
Why am I wrong?
The correct answer is 35.2 J
 

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Better check your units. Also, you determined the stored energy per unit volume.
 
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Chestermiller said:
Better check your units. Also, you determined the stored energy per unit volume.
Thanks!
 

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