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.

Below is an attachment containing the solution.

Answer;

High temperature and pressure

Explanation;Nuclear fusion in stars and supernovae is the primary process by which new natural elements are created. Nuclear fusion occurs in presence of very high temperature and high pressure, which one of the common characteristics of many stars.High temperature gives hydrogen atoms enough energy to overcome the electrical repulsion between the protons. Fusion requires temperatures about 100 million Kelvin.  High pressure squeezes the hydrogen atoms together. For example the sun uses its mass and the force of gravity to squeeze hydrogen atoms together in its core.