The value of Young's modulus for a perfectly rigid body is ...........

Two persons pull a wire towards themselves. Each person exerts a force of $200 \mathrm{~N}$ on the wire. Young's modulus of the material of wire is $1 \times 10^{11} \mathrm{~N} \mathrm{~m}^{-2}$. Original length of the wire is $2 \mathrm{~m}$ and the area of cross section is $2 \mathrm{~cm}^2$. The wire will extend in length by . . . . . . . .$\mu \mathrm{m}$.

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 find the increase in length of this wire.

A wire is stretched by $0.01$ $m$ by a certain force $F.$ Another wire of same material whose diameter and length are double to the original wire is stretched by the same force. Then its elongation will be

The following four wires of length $L$ and radius $r$ are made of the same material. Which of these will have the largest extension, when the same tension is applied?

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