Question

Hooke’s law states that stress strain.

a) What is the necessary condition for the

above law to be valid?

b) Explain with the help of a graph, the

relation between stress and strain for a given

solid material under increasing tensile stress.

Answer 1

stress is directly proportion to strain

Answer 2

Answer:

Hooke's law: This law states that within the elastic limit the stress is directly proportional to the strain produced.

Explanation:

(a) Hooke's law: This law states that within the elastic limit the stress is directly proportional to the strain produced.

Therefore, Hooke's law is valid within the elastic limit.

(b)

• This graph helps us to grasp how a given material deforms with increasing loads. The curve between O and A is a line and this signifies stress is directly ∝proportional to strain.
• In the region between points O and A the material behaves like an elastic body.
• In the region from A to B, stress is not directly proportional to the strain. And the material returns to its original position after the force is removed. They exhibit elastic properties.
• Point B in the curve is called the yield point which means that till this point the material is elastic and the stress corresponding to point B is called the yield strength of the material.
• The region from points O and B is known as the Elastic region.
• From point B to point D the strain rapidly increases even for a little change in stress.
• When the force is removed the material does not come back to its initial position.  At this point, since the body changed its shape, the stress is zero but the strain is not equal to zero.
• The material has undergone plastic deformation.
• The material is said to be permanently set.
• Point D on the graph is known as the ultimate tensile strength (Su) of the material.
• From D to E, the stress decreases even if the strain increases.

• Finally at point E fracture occurs. This means the body breaks.

Hooke's law: This law states that within the elastic limit the stress is directly proportional to the strain produced.

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