Q1: Thermal shock produced by cooling is more dengerous/deleterious than that produced by heating a surface, because of the reason that

ANS:A - cooling produces tension on the surface.

Thermal shock produced by cooling is more dangerous/deleterious than that produced by heating a surface because cooling produces tension on the surface. When a surface is rapidly cooled, such as by quenching in water or air, the outer layers contract and cool faster than the interior, resulting in the development of tensile stresses on the surface. These tensile stresses can lead to cracking or fracture of the material, particularly if it is brittle or if the temperature gradient is severe. In contrast, when a surface is heated, it typically expands, and the outer layers experience compressive stresses. While heating can also induce thermal stresses, the magnitude of these stresses is generally lower compared to those generated during rapid cooling. Additionally, materials often have greater tolerance for compression than tension, making cooling-induced thermal shock more detrimental.