The load versus elongation graphs for four wires of same length and made of the same material are shown in the figure. The thinnest wire is represented by the line

$A$ lift is tied with thick iron ropes having mass $M$. The maximum acceleration of the lift is $a \ m/s^2$ and the maximum safe stress is $s \ N/m^2$. The minimum diameter of the rope is $(g = \text{acceleration due to gravity})$

The elastic behaviour of a material for linear stress and linear strain is shown in the figure. The energy density for a linear strain of $5 \times 10^{-4}$ is $\dots \; kJ/m^3$. Assume that the material is elastic up to the linear strain of $5 \times 10^{-4}$.

The breaking stress of aluminium is $7.5 \times 10^7 \,N m^{-2}$. The greatest length of aluminium wire that can hang vertically without breaking is ......... $\times 10^3 \,m$ (Density of aluminium is $2.7 \times 10^3 \,kg m^{-3}$ and $g = 9.8 \,m s^{-2}$)

If the length of a wire is doubled,what is the strain?

The lower surface of a cube is fixed. On its upper surface,a force is applied at an angle of $30^{\circ}$ from its surface. The change will be of the type: