A particle of mass m is projected with a speed u from the ground at an angle θ=(π)/3 w.r.t. horizontal ( x -axis). When it has reached its maximum…

A particle of mass $\displaystyle m$ is projected with a speed $\displaystyle u$ from the ground at an angle $\displaystyle \theta=\frac{\pi}{3}$ w.r.t. horizontal ( $\displaystyle x$-axis). When it has reached its maximum height, it collides completely inelastically with another particle of the same mass and velocity $\displaystyle \mathrm{u} \hat{i}$. The horizontal distance covered by the combined mass before reaching the ground is :