Question

Two trains, each of length 100 m, moving in opposite directions along parallel lines, meet each other with speeds of 50 $km{h}^{-1}$ and 40 $km{h}^{-1}$. If their accelerations are 30 $cm{s}^{-2}$ and 20 $cm{s}^{-2}$, respectively, find the time they will take to pass each other.

Answer 1

D=$100+100=200$m

$a_{relative}$=$\frac{1}{2}m/s^2$

S=$ut+\frac{1}{2}{at}^2$

$V_{relative}=90km/h=90\times \frac{5}{18}=25m/s$

$200=25t+\frac{1}{2}\times \frac{1}{2}\times t^2$

$t=7.45$sec