What is Young's modulus? Explain it,and provide its unit and dimensional formula.

(N/A) Experimental observations show that for a given material,the magnitude of the strain produced is the same whether the stress is tensile or compressive.
The ratio of tensile (or compressive) stress $(\sigma)$ to the longitudinal strain $(\varepsilon)$ is defined as Young's modulus and is denoted by the symbol $Y$.
$\text{Young's modulus} = \frac{\text{Tensile stress } (\sigma)}{\text{Longitudinal strain } (\varepsilon)}$
$Y = \frac{\sigma}{\varepsilon}$
$\therefore Y = \frac{(F / A)}{(\Delta L / L)} = \frac{(F \times L)}{(A \times \Delta L)}$
Since strain is a dimensionless quantity,the unit of Young's modulus is the same as that of stress,which is $N \ m^{-2}$ or Pascal $(Pa)$.
Dimensional formula: $[M^1 L^{-1} T^{-2}]$.
Young's moduli,elastic limit,and tensile strength of some materials are given below:

Substance	Young's Modulus $(10^9 \ N/m^2)$	Elastic limit $(10^7 \ N/m^2)$	Tensile strength $(10^7 \ N/m^2)$
Aluminium	$70$	$18$	$20$
Copper	$120$	$20$	$40$
Iron (Wrought)	$190$	$17$	$33$
Steel	$200$	$30$	$50$
Bone (Tensile/Compressive)	$16 / 9$	-	$12 / 12$

For metals,Young's moduli are large; therefore,these materials require a large force to produce a small change in length.
Steel is more elastic than copper,brass,and aluminium. It is for this reason that steel is preferred in heavy-duty machines and in structural designs.
Wood,bone,concrete,and glass have rather small Young's moduli.