Question

Breaking stress of a material is $2\times {10}^{8}N/m^2$. What maximum length of the wire of this material can be so that the wire does not break my own weight? [Density of material $=5\times {10}^{3}kg/m^3$]

• A. $1km$
• B. $2km$
• C. $3km$
• D. $4km$

Answer 1

The correct option is D $4km$

Let length $=L$

So, mass of length $L=$( Density of wire) (volume of wire)

Density of wire $=\rho =5\times {10}^{3}Kg/m^3$

Volume $=LA(A=$ Area of cross section $)$

$Stress=\frac{Force}{Area}$

$2\times {10}^8=\frac{mg}{A}=\frac{\rho LAq}{A}$

So, $L=\frac{2\times {10}^8}{\rho \times g}$

$=\frac{2\times {10}^8}{5\times {10}^3\times 10}$

$L=4000m$

$L=4km$

option $\left(d\right)$