Question

Question #081c9

Answer 1

See below.

Explanation:

The idea behind elasticity is that no object is perfectly rigid; all objects deform when subjected to a force, even if it is by such a small amount that we cannot see it.

For example, many people are surprised to hear about materials like steel being stretched. We might think of such materials as completely rigid, completely non-elastic, but this is not the case. In fact, this is something of great concern to engineers, for instance, when they are designing buildings, bridges, etc.

The deformation of the object is called the strain, and the force which causes that deformation is called the stress, i.e. stress causes strain. Different types of force that might be applied to an object include stretching, squeezing, twisting, etc.

Hooke's law of elasticity tells us that the ratio of stress to strain is constant, and that constant is called the elastic modulus of the object.

• All objects which obey Hooke's law are called elastic
• The elasticity of an object is characterized by its elastic modulus
• The smaller the elastic modulus, the "easier" it is to stretch/squeeze/twist/etc.

There are three types of elastic moduli:

• Young's modulus (Y)—tensile stress/strain, "stretching"
• Shear modulus (S)—shear stress/strain, "twisting"
• Bulk modulus (B) volumetric stress/strain, "squeezing/compressing"

As far as where the elasticity of an object originates, this comes down to the atomic level with the bonds between the atoms making up the object. We often use the analogy that these bonds are like springs, which we can think of as being stretched or compressed.