The increase in length is $l$ of a wire of length $L$ by the longitudinal stress. Then the stress is proportional to

Distinguish between a liquid body and a solid body.

The ratio of radii of two wires of same material is $2: 1$. If these wires are stretched by equal force,the ratio of stresses produced in them is .............

Check if the following statements are True or False:
$(a)$ Shear modulus of liquid is infinite.
$(b)$ For a given load (external force),steel is more deformed than rubber.
$(c)$ When a solid body is beaten,rolled,heated,or cooled,its elastic properties are affected.

For what reasons can the elastic behavior of a solid body be explained?

$A$ rod is placed on a smooth horizontal surface. What is the stress developed when the temperature is increased by $40\,^{\circ}C$?
$[\alpha = 5\, \times\, 10^{-5}\,^{\circ}C^{-1},\, Y = 5\, \times\, 10^{11}\, N/m^2]$