One end of a uniform wire of length $L$ and weight $W$ is attached rigidly to a point in the roof,and a weight $W_1$ is suspended from its lower end. If $S$ is the area of cross-section of the wire,the stress in the wire at a height $3L/4$ from its lower end is

Is it possible to double the length of a metallic wire by applying force over it?

Two identical solid balls,one of ivory and the other of wet-clay,are dropped from the same height on the floor. Which one will rise to a greater height after striking the floor and why?

The material which practically does not show elastic after effect is

Wires $W_{1}$ and $W_{2}$ are made of the same material having a breaking stress of $1.25 \times 10^{9} \, N/m^{2}$. $W_{1}$ and $W_{2}$ have cross-sectional areas of $8 \times 10^{-7} \, m^{2}$ and $4 \times 10^{-7} \, m^{2}$,respectively. Masses of $20 \, kg$ and $10 \, kg$ hang from them as shown in the figure. The maximum mass $m$ that can be placed in the pan without breaking the wires is $..... \, kg$. (Use $g = 10 \, m/s^{2}$)

In solids,inter-atomic forces are