In which case is there maximum extension in the wire,if the same force is applied to each wire?

$A$ wire of length $L$ and radius $r$ is clamped rigidly at one end. When the other end of the wire is pulled by a force $f$,its length increases by $l$. Another wire of the same material of length $2L$ and radius $2r$ is pulled by a force $2f$. Then the increase in its length will be

$A$ metal wire with circular cross-section and length $1 \,m$ is pulled with a tensile force of $1000 \,N$ on each side. For the wire to be stretched not more than $0.25 \,cm$, the minimum diameter of the wire required is (Young's modulus of the metal $= 10^{11} \,Pa$, take $\sqrt{\pi} = 1.77$). (in $\,mm$)

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

Consider a rod of length $1.0 \ m$ with a cross-sectional area of $0.50 \ cm^2$. The rod supports a $500 \ kg$ platform that hangs attached to the rod's lower end. What is the elongation of the rod under the stress,ignoring the weight of the rod (in $mm$)? Consider Young's modulus to be $10^{11} \ Pa$ and $g = 10 \ m \ s^{-2}$.

Two wires of the same length and material are stretched by the same force. If their masses are in the ratio $3:4$,then the ratio of their elongations is