Mark the wrong statement.

If the breaking stress of a wire is $3.18 \times 10^{10} \, N/m^2$,what should be its minimum radius so that the wire does not break? (Refer to the figure for the masses attached to the pulley system,assume $g = 10 \, m/s^2$)

Match the following:

Column-$I$	Column-$II$
$(A)$ Shear modulus	$(I)$ Resistance to change in volume
$(B)$ Shearing stress	$(II)$ Proportionality constant
$(C)$ Elastic fatigue	$(III)$ Tangential stress
$(D)$ Modulus of elasticity	$(IV)$ Temporary loss of elastic property
	$(V)$ Resistance to change against deformation force

The correct match is:

Two identical wires of rubber and iron are stretched by the same weight. The number of atoms in the iron wire will be:

$A$ wire of length $5 \,m$ is twisted through $30^{\circ}$ at its free end. If the radius of the wire is $1 \,mm$,the shearing strain in the wire is: (in $^{\circ}$)

$A$ string of length $0.314 \text{ m}$ and Young's modulus $2 \times 10^{10} \text{ N/m}^2$ is connected to another string of length $B$ and Young's modulus both twice of those of $A$. This series combination of strings is then suspended from a rigid support and its free end is fixed to a load of mass $0.8 \text{ kg}$. The net change in length of the combination is . . . . . . $\text{mm}$. (radius of both the strings is $0.2 \text{ mm}$ and acceleration due to gravity $= 10 \text{ m/s}^2$) (Mass of both strings is to be neglected as compared to the mass of load)