Question

Assertion: Young's modulus, Shear modulus and Bulk modulus are used to describe the elastic behaviour of objects as they respond to deforming forces that act on them. Reason: Young's modulus and Shear modulus are relevant only for solids. Bulk modulus is relevant for solids, liquid, and gases.

Assertion: Metals have larger values of Young's modulus than alloys and elastomers. Reason: A material with large value of Young's modulus requires a small force to produce large changes in its length.

The stress-strain curves vary from material to material. These curves help us to understand how a given material deforms with increasing loads. 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. The body regains its original dimensions when the applied force is removed. In this region, the solid behaves as an elastic body.

A bridge must be designed such that it can withstand the load of the flowing traffic, the force of winds and its own weight. Similarly, in the design of buildings the use of beams and columns is very common. In both the cases, the overcoming of the problem of bending of beam under a load is of prime importance. The beam should not bend too much or break. A bar of length l, breadth b, and depth d when loaded at the centre by a load W sags by an amount given by δ = Wl3/(4bd3Y)