The dimensional formula for Young's modulus is

The dimensions of four wires of the same material are given below. The increase in length is maximum in the wire of

$A$ copper wire $(Y = 1 \times 10^{11} \, N/m^2)$ of length $6 \, m$ and a steel wire $(Y = 2 \times 10^{11} \, N/m^2)$ of length $4 \, m$,each of cross-sectional area $10^{-5} \, m^2$,are fastened end to end and stretched by a tension of $100 \, N$. The elongation produced in the copper wire is ......... $mm$.

Write the equation of bending in a rod. Write the unit of bending and its dimensional formula.

Two rods of different materials having coefficients of linear expansion $\alpha_1, \alpha_2$ and Young's moduli $Y_1$ and $Y_2$ respectively are fixed between two rigid massive walls. The rods are heated such that they undergo the same increase in temperature. There is no bending of rods. If $\alpha_1 : \alpha_2 = 2 : 3$,and the thermal stresses developed in the two rods are equal,then the ratio $Y_1 : Y_2$ is equal to:

The speed of a transverse wave travelling in a wire of length $50 \text{ cm}$,cross-sectional area $1 \text{ mm}^2$ and mass $5 \text{ g}$ is $80 \text{ ms}^{-1}$. The Young's modulus of the material of the wire is $4 \times 10^{11} \text{ Nm}^{-2}$. The extension in the length of the wire is