$P$ is a point moving with constant speed $10 \mathrm{~m} / \mathrm{s}$ such that its velocity vector always maintains an angle $60^{\circ}$ with line $O P$ as shown in figure $(O$ is a fixed point in space). The initial distance between $O$ and $P$ is $100 \mathrm{~m} . \Lambda$ fter what time shall $p$ reach $O ?$