Name: Properties of Solid
Uploaded: 2019-07-19
Duration: 3 min 59 s
Description: Do you know which are the important mechanical properties of solids? In this video, we will discuss the solid state of matter and its different properties.

Question

Define Hooke's Law of elasticity, proportionality, permanent set and breaking stress.

Accepted Answer

Hooke's law of elasticity states that for small deformation (within proportionality limit) the stress is directly proportional to strain. The constant of proportionality is called the modulus of elasticity.

Consider the typical stress-strain curve for a material. . From the graph, we can see that in the region between O to A, the curve is linear. In this region, Hooke’s law is obeyed. In the region from A to B, stress and strain are not proportional. But, the body still returns to its original dimension when the load is removed. The point B in the curve is known as yield point (also known as elastic limit) and the corresponding stress is known as yield strength of the material. If the load is increased further, the stress developed exceeds the yield strength and strain increases rapidly even for a small change in the stress. The portion of the curve between B and D shows this. When the load is removed, say at some point C between B and D, the body does not regain its original dimension. In this case, even when the stress is zero, the strain is not zero. The material is said to have a permanent set. The deformation is said to be plastic deformation.

Breaking stress is the maximum force that can be applied on a cross-sectional area of a material in such a way that the material is unable to withstand any additional amount of stress before breaking. This is corresponding to point E in the graph.

Define Hooke's Law of elasticity, proportionality, permanent set and breaking stress.

Important Questions on Mechanical Properties of Solids

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