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Two identical circular rods of same diameter and same length are subjected to same magnitude of axial tensile force. One of the rods is made out of mild steel having the modulus of elasticity of 206 GPa. The other rod is made out of east iron having the modulus of elasticity of 100 GPa. Assume both the materials to be homogeneous and isotropic and the axial force causes the same amount of uniform stress in both the rods. The stresses developed are within the proportional limit of the respective materials. Which of the following observations is correct?
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- Both rods elongate by the same amount
- Mild steel rod elongates more than the cast iron
- Cast iron rod elongates more than the mild steel rod
- As the stresses are equal strains are also equal in both the rods
- Both rods elongate by the same amount
Correct Option: C
Emild steel = 206 GPa
Ecast iron = 100 GPa
Now,
| Elongation in cast iron, ∆CI = |  |  | ||
| AE | CI |
| Elongation in mild steel, ∆m.s. = | | | ||
| AE | M.S. |
| ⇒ | = | ||
| AEC.I. | |||
| ∆M.S. | |||
| AE M.S. |
| = | = 2.06 | |||
| EC.I. | 100 |
∴ ∆C.I. > ∆M.S.
