Question

Two trains A and B, 100m and 60m long,are moving in opposite directions on parallel tracks.The velocity of the shorter trains is 3 times that of the longer one.If the trains take 4s to cross each other, the velocities of the trains are

Answer 1

let us assume that the longer train is stopped.then the velocity of shorter train w.r.t longer train is 4V

$\therefore t=\frac{160}{4V}$

$V=\frac{160}{4t}=\frac{160}{4\times 4}=10m/s$

now $3V=3\times 10=30\frac{m}{s}$