Question

The breaking stress for a substance is $10^{6} \,N / m ^{2}$. What length of the wire of this substance should be suspended vertically so that the wire breaks under its own weight? (Given: density of material of the wire $=4 \times 10^{3} kg / m ^{3}$ and $g=10 \,m s ^{-2}$ )

• A. 10 m
• B. 15 m
• C. 25 m
• D. 34 m

Answer 1

Answer: (C)

Breaking stress $=\frac{\text { Maximum weight }}{\text { Area of cross section }}$
$10^{6}=\frac{\text { al } \rho g}{a}=l \rho g$
or $l=\frac{10^{6}}{\rho g}=\frac{10^{6}}{4 \times 10^{3} \times 10} m =25\, m$