Each of three blocks P, Q and R shown in figure has a mass of 3 kg. Each of the wires A and B has cross-sectional area 0.005 cm^2 and Young's modulus…

Each of three blocks $\displaystyle P, Q$ and $\displaystyle R$ shown in figure has a mass of $\displaystyle 3$ kg . Each of the wires $\displaystyle A$ and $\displaystyle B$ has cross-sectional area $\displaystyle 0.005 \mathrm{~cm}^2$ and Young's modulus $\displaystyle 2 \times 10^{11} \mathrm{~N} \mathrm{~m}^{-2}$. Neglecting friction, the longitudinal strain on wire $\displaystyle B$ is $\displaystyle \_\_\_\_$ $\displaystyle \times 10^{-4} .\left(\right.$ Take $\displaystyle \left.\mathrm{g}=10 \mathrm{~m} / \mathrm{s}^2\right)$