Two trains, each $30 \mathrm{~m}$ long are travelling in opposite directions with velocities $5 \mathrm{~m}…
Two trains, each $30 \mathrm{~m}$ long are travelling in opposite directions with velocities $5 \mathrm{~m} / \mathrm{s}$ and $10 \mathrm{~m} / \mathrm{s}$. They will cross after
$4 \mathrm{~s}$
$3 \mathrm{~s}$
$2 \mathrm{~s}$
$1 \mathrm{~s}$
Solution
Relative velocity of one train w. r. t other $=5+10$
$=15 \mathrm{~m} / \mathrm{s}$
Total length to cross $(\mathrm{L})=30+30=60 \mathrm{~m}$
$\therefore \quad t=\frac{L}{V}=\frac{60}{15}=4 s$