A steel bar of 2 m length is fixed at both ends at 20°C. The coefficient of thermal expansion is 11 x 10-6/°C and the modulus of the elasticity is 2 x 106 kg/cm2. If the temperature is changed to 18°C, then the bar will be experience a stress of

A. 22 kg/cm2 (tensile) B. 22 kg/cm2 (compressive) C. 44 kg/cm2 (compressive) D. 44 kg/cm2 (tensile)

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Answers

2014-08-14T01:44:26+05:30

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ΔL = L * α * ΔT = 2 * 11 * 10^-6 * -2  = - L * 22 * 10^-6 meters

Y = Stress / Strain   =>   Stress = Strain  * Y
Stress = Y * ΔL / L  = - 2 * 10^6 * 10^4  * 22 * 10^-6  = - 44 * 10^4 N
     = - 440 Kilo Newtons / meter²
     = - 44 N/cm² 
Compressive as Stress is -ve.

ANswer is C

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