Two wires are made of the same material and have the same volume. The first wire has cross-sectional area $A$ and the second wire has cross-sectional area $3A$. If the length of the first wire is increased by $\Delta l$ on applying a force $F$, how much force is needed to stretch the second wire by the same amount?

A rubber cord $10\, m$ long is suspended vertically. How much does it stretch under its own weight $($Density of rubber is $1500\, kg/m^3, Y = 5×10^8 N/m^2, g = 10 m/s^2$$)$

The diameter of a brass rod is 4 mm and Young's modulus of brass is $9 \times {10^{10}}\,N/{m^2}$. The force required to stretch by $0.1\%$ of its length is

The force required to stretch a wire of crosssection $1 cm ^{2}$ to double its length will be …….. $ \times 10^{7}\,N$

(Given Yong's modulus of the wire $=2 \times 10^{11}\,N / m ^{2}$ )

The ratio of the lengths of two wires $A$ and $B$ of same material is $1 : 2$ and the ratio of their diameter is $2 : 1.$ They are stretched by the same force, then the ratio of increase in length will be