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)

C. 44 kg/cm2 (compressive).

Explanation:

The main difference between tensile and compressive stress is that tensile stress results in elongation whereas compressive stress results in shortening.

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it is given that trillions of microbes make up to 1% to 3% of the body mass.

let's take average of this percentage: 2%

consider the average mass of the human body as 70 kg.

then, trillions of microbes would have mass  

therefore, 100 trillion micro-organisms would weigh:

this is an approximate value and could change depending on the mass of the human body and percentage of the microbes present in it.

average mass per microorganism =