As shown in the figure, a particle of mass 10 kg is placed at a point $A$. When the particle is slightly displaced to its right, it starts moving and reaches the point $B$. The speed of the particle at $B$ is $x \mathrm{m} / \mathrm{s}$. (Take $\mathrm{g}=10 \mathrm{~m} / \mathrm{s}^2$ ) The value of ' x ' to the nearest integer is $\_\_\_\_$