A body starting from rest moves along a straight line with a constant acceleration. The variation of speed $\left(v\right)$ with distance $\left(s\right)$ is represented by the graph:

In $1.0 \sec$ a particle goes from point $A$ to point $B$ moving in a semicircle of radius $1.0 \mathrm{m}.$ The magnitude of average velocity is

$50 \mathrm{m}$ long trains are crossing each other in opposite direction with velocity of $10 \mathrm{m} {\mathrm{s}}^{-1}$ and $15 \mathrm{m} {\mathrm{s}}^{-1}$ respectively. Then time-taken by trains to cross each other will be