In steel, the Young’s modulus and the strain at the breaking point are 2 x 10¹¹ Nm⁻² and 0.15 respectively. The stress at the breaking point for steel is therefore

To find the stress at the breaking point for steel, we can use Hooke's Law, which relates stress, strain, and Young's modulus of elasticity.

Hooke's Law is mathematically expressed as:
$\mathrm{Young\text{'}s\; Modulus}\left(Y\right)=\frac{\mathrm{Stress}}{\mathrm{Strain}}$
From this relationship, we can solve for stress:
$\mathrm{Stress}=\mathrm{Young\text{'}s\; Modulus}\times \mathrm{Strain}$

We are given the following values:
Young’s modulus ($Y$) = $2\times {10}^{11}{\mathrm{Nm}}^{-2}$
Strain at the breaking point = $0.15$

Substitute these values into the equation to calculate the breaking stress:
$\mathrm{Stress}=(2\times {10}^{11}{\mathrm{Nm}}^{-2})\times 0.15$
$\mathrm{Stress}=0.3\times {10}^{11}{\mathrm{Nm}}^{-2}$
$\mathrm{Stress}=3\times {10}^{10}{\mathrm{Nm}}^{-2}$

Therefore, the stress at the breaking point for steel is $3\times {10}^{10}{\mathrm{Nm}}^{-2}$.