. A thick walled glass tumbler sometimes cracks when boiling water is poured into it. Why? .Give reason.
Answers
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There are a number of factors involved in the given scenario of this question. When a piece of thick glass is placed in hot water the external surface will be heated and hence it will try to expand. On the other hand, the internal surface is not heated creating both tension and compression forces in different areas. Glass is strong in compression but not much stronger in tension so there is a dynamic that is resolved by the thickness and hence strength of the glass.-Thin glass is relatively weaker, but also more flexible and hence can bear more stress. The stress created by the hot water can cause the glass to bend to relieve the pressures on it. It does so without breaking.Thus, we can conclude that the stronger thick glass experiences greater forces than the inner thin and weaker glass. Whether the glass does, or does not, crack depends on the temperature differential, the thickness of the glass, it's Young's modulus, tensile strength, presence-or absence- of stress risers and some other even less quantifiable properties.So, a thick glass breaks when hot water is poured into it.
Note:As the surface of glass that comes in contact with the hot liquid, it heats up and expands as per its coefficient of thermal expansion. Thin glasses are more likely to withstand the stress developed due to heat.