Question

On increasing the length by $0.5mm$ in a steel wire of length $2m$ and area of cross-section $2c{m}^2$, the force required is [$Y$ for steel $=2.2\times {10}^{11}N/m^2$]:

• A. $1.1\times {10}^{5}N$
• B. $1.1\times {10}^{4}N$
• C. $1.1\times {10}^{3}N$
• D. $1.1\times {10}^{2}N$

Answer 1

The correct option is C $1.1\times {10}^{3}N$

Force, $F=\frac{YA\Delta l}{L}=\frac{2.2\times {10}^{11}\times 2\times {10}^{-4}\times 0.5\times {10}^{-3}}{2}=1.1\times {10}^{3}N$