Question
A bird is at a point P whose coordinates are $(4 m,-1 m, 5 m)$. The bird observes two points $P _1$ and $P _2$ having coordinates $(-1 m, 2 m, 0 m)$ and $(1 m, 1 m, 4 m)$ respectively. At time $t =0$, it starts flying in a plane of three positions, with a constant speed of $5 ms^{-1}$ in a direction perpendicular to the straight line $P _1 P _2$ till it sees $P _1$ and $P _2$ collinear at time $t$. Calculate $t$.
