(i) State Hook's law.
(ii) Draw a labelled graph of tensile stress against tensile strain for a metal wire upto the breaking point. Shhow on your graph the region in which Hooke's law is obeyed.
What is the significance of the area between the graph and the strain axis withing the Hooke's law region?

The stress strain graph for a metal wire is as shown in the figure. In the graph, the region in which Hooke's law is obeyed, the ultimate strength and fracture are represented by

The graph show the behaviour of a length of wire in the region for which the substances obeys Hooke's law. P and Q represent

Figure shows the relationship between tensile stress and strain for a typical material. Below proportional point A, stress is directly proportional to strain which means Young's moudulus (Y) is a constant. In this region the material obeys Hooke's law. Provided the strain is below the yield point 'B' the material returns to its original shape and size when the force is removed. Beyond the yield point, the material retains a permancnt deformation after the stress is removed. For stresses beyond the yeld point, the material exhibit plastic flow, which means that it continues to elongate for little increases in the stress. Beyond C a local constriction occurs. The material fractures at D (i.e. breaking point). The graph below shows the stress-strain curve for 4 different materials. Material which is good for making wires by stretching is

Figure shows the relationship between tensile stress and strain for a typical material. Below proportional point A, stress is directly proportional to strain which means Young's moudulus (Y) is a constant. In this region the material obeys Hooke's law. Provided the strain is below the yield point 'B' the material returns to its original shape and size when the force is removed. Beyond the yield point, the material retains a permancnt deformation after the stress is removed. For stresses beyond the yeld point, the material exhibit plastic flow, which means that it continues to elongate for little increases in the stress. Beyond C a local constriction occurs. The material fractures at D (i.e. breaking point). The graph below shows the stress-strain curve for 4 different materials. If you bough a new shoe which bites in the beginning and later on fits perfectly, then the material used to making the shoe is

Figure shows the relationship between tensile stress and strain for a typical material. Below proportional point A, stress is directly proportional to strain which means Young's moudulus (Y) is a constant. In this region the material obeys Hooke's law. Provided the strain is below the yield point 'B' the material returns to its original shape and size when the force is removed. Beyond the yield point, the material retains a permancnt deformation after the stress is removed. For stresses beyond the yeld point, the material exhibit plastic flow, which means that it continues to elongate for little increases in the stress. Beyond C a local constriction occurs. The material fractures at D (i.e. breaking point). The graph below shows the stress-strain curve for 4 different materials. If you bough a new shoe which bites in the beginning and later on fits perfectly, then the material used to making the shoe is

Figure shows the relationship between tensile stress and strain for a typical material. Below proportional point A, stress is directly proportional to strain which means Young's moudulus (Y) is a constant. In this region the material obeys Hooke's law. Provided the strain is below the yield point 'B' the material returns to its original shape and size when the force is removed. Beyond the yield point, the material retains a permancnt deformation after the stress is removed. For stresses beyond the yeld point, the material exhibit plastic flow, which means that it continues to elongate for little increases in the stress. Beyond C a local constriction occurs. The material fractures at D (i.e. breaking point). The graph below shows the stress-strain curve for 4 different materials. If you bough a new shoe which bites in the beginning and later on fits perfectly, then the material used to making the shoe is

Assertion : For small deformations, the stress and strain are proportional to each other. Reason: A class of solids called elastomers does not obey Hooke's law.

The graph shows the behaviour of a steel wire in the region for whoch the wire obeys Hooke's law. The graph is a parabola. The variables X and Y -axes, respectively can be [ stress (sigma) ,strain ( epsilon) and elastic potential energy(U) ]

Assertion Upto elastic limit of a stress-strain curve, the steel wire tends to regain its original shape when stress is removed. Reason Within elastic limit, the wire follows Hooke's law.

The stress strain graph for a metal wire is shown in the fig. Up to the point E, the wire returns to its original state O along the curve EPO, when it is gradually unloaded. Point B corresponds to the fracture of the wire. (a) Up to what point on the curve is Hooke's law obeyed? (this point some times called proportional limits). (b) Which point on the curve corresponding to elastic limit or yield point of the wire? (c ) Indicate the elastic and plastic regions of the stress-strain graph. (d) Describe what happens when the wire is loaded up to a stress corresponding to the point A on the graph and then unloaded gradually. In particular explain the dotted curve. (e) What is peculiar about the portion of the stress- strain graph from C to B? Up to what stress can the wire be subjected without causing fracture?