Compressive and tensile forces - class-XII

More elastic the material, higher the Young's Modulus.
Young's Modulus of Steel = 200 GPa
Young's Modulus of Rubber = 0.01-0.1 GPa
Young's Modulus of Steel is much higher than Rubber, So steel is more elastic than rubber.

Y = FL/Al
Y - Young's Modulus
L - Actual Length
A - Cross Section Area
l - Elongation

l = FL/AY
keeping F,L,A constant 
l is inversely proportional to Y
Hence, Higher the Young's Modulus lesser the deformation (for Different Materials)

If a force on a body changes the normal positions of the molecules of a body, resulting in a change in the configuration of the body, then the force applied is called deforming force and change in shape of the body is called deformation. 

Deformation of a body is the change in shape of a body caused by the application of stress. According to the Hooke's law, the deformation caused in an elastic material is directly proportional to the stress applied to it.

Cranes and other heavy machinery need to be rested to prevent overheating and mechanical fatigue, making the statement true.

Elastic fatigue is defined as the temporary loss of elastic properties of a material by applying repeated force on the material. If there is no sufficient time between repeated force application, then a permanent deformation remain there in each time of applying force.

Bulk modulus $=\cfrac { P }{ \Delta V/V } $
Compressibility$=\cfrac { 1 }{ Bulk\quad modulus } =\cfrac { \Delta V/V }{ P } =K\quad \quad $(Compressibility)

Creep is a situation in which a component experiences deformation with time as it is put into use. Best example to illustrate this is that electrical cables are taught(tight) when they are installed but after some time they experience sagging due to self weight.

The correct option is option (c)

The stress at any point is the force acting on the cross-section divided by the area S. At a height 3L/4 from the bottom, the weight supported is the suspended weight W1 plus the weight of the wire segment below that point, which is (3/4)W. Thus, the total force is W1 + (3/4)W, and stress is (W1 + 3W/4)/S.

An elastic metal rod will change its length when it is pulled along its length by a force acting at one end or rotates about an axis at one end. Since, deforming force exceeds the elastic limit.

$\dfrac{{stress}}{{strain}} = y$

In well-designed steel frame structures, inelastic deformation under severe seismic loading is confirmed in beam plastic hinges located near the beam-to-column connections. Thus, deformation capacity of the plastic hinge and resilience of the connections are essential for good plastic behavior and expected energy dissipation in steel frame structures. This essential plastic behaviour at the hinge is strongly influenced by the difference of material properties. Generally, the material properties are specified in terms of yield stress and/or ultimate strength. However, the characteristics of the materials are not defined by only these properties. Thus, the characteristics of various materials aren’t reflected in present building codes, particularly on deformation capacity classification.