$A$ steel rod has a radius of $20\,mm$ and a length of $2.0\,m$. $A$ force of $62.8\,kN$ stretches it along its length. Young's modulus of steel is $2.0 \times 10^{11}\,N/m^2$. The longitudinal strain produced in the wire is $..........\times 10^{-5}$.

Two uniform rods $AB$ and $BC$ have Young's moduli $1.2 \times 10^{11} \, N/m^2$ and $1.5 \times 10^{11} \, N/m^2$ respectively. If the coefficient of linear expansion of $AB$ is $1.5 \times 10^{-5} /^{\circ}C$ and both have equal area of cross-section,then the coefficient of linear expansion of $BC$,for which there is no shift of the junction at all temperatures,is ............. $\times 10^{-5} /^{\circ}C$.

Two wires made of the same material are clamped rigidly at one end and pulled by the same force on the other end. The length and the radius of the first wire are three times those of the second wire. If $x$ is the increase in the length of the first wire,then the increase in the length of the second wire is

Explain the experimental determination of Young's modulus.

Two blocks of mass $2 \ kg$ and $4 \ kg$ are connected by a metal wire going over a smooth pulley as shown in the figure. The radius of the wire is $4.0 \times 10^{-5} \ m$ and Young's modulus of the metal is $2.0 \times 10^{11} \ N/m^2$. The longitudinal strain developed in the wire is $\frac{1}{\alpha \pi}$. The value of $\alpha$ is [Use $g = 10 \ m/s^2$].

The unit of Young's modulus is