At a certain height, a body at rest explodes into two equal fragments with one fragment receiving a horizontal velocity of $10 \sqrt{3} \mathrm{~ms}^{-1}$. The horizontal distance between the two fragments, when their displacement vectors are inclined at $60^{\circ}$ relative to each other is $\left(\mathrm{g}=10 \mathrm{~ms}^{-2}\right)$