Four identical rods are stretched by the same force. The maximum extension is produced in:

Two metallic wires $P$ and $Q$ have the same volume and are made up of the same material. If their areas of cross-section are in the ratio $4:1$ and a force $F_1$ is applied to $P$,an extension of $\Delta l$ is produced. The force required to produce the same extension in $Q$ is $F_2$. The value of $\frac{F_1}{F_2}$ is . . . . . . .

$A$ steel wire $1.5\,m$ long and of radius $1\,mm$ is attached with a load of $3\,kg$ at one end,while the other end is fixed. It is whirled in a vertical circle with a frequency of $2\,Hz$. Find the elongation of the wire when the weight is at the lowest position. (Given: $Y = 2 \times 10^{11}\,N/m^2$ and $g = 10\,m/s^2$)

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

$A$ thick metal wire of density $\rho$ and length $L$ is hung from a rigid support. The increase in length of the wire due to its own weight is ($Y =$ Young's modulus of the material of the wire).

To double the length of an iron wire having $0.5 \, cm^2$ area of cross-section,the required force will be $(Y = 10^{12} \, dyne/cm^2)$.