Two trains A and B of length 400 m each are moving on two parallel tracks with a uniform speed of `72 km h^(-1)` in the same direction, with A ahead of B. The dirver of B decides to overtake A and accelerates by `1 ms^(-2)`. If after 50s, the guard of B just brushed past the driver of A, what was the original distance between them ?

Explanation

Velocity of train `A=72km h^(-1)=(72xx1000)/(3600)`
`=20ms^(-1)`
Velocity of train `B=20m//s,t=50s, a=0`
`S_(A)`=Distance covered by train A in 50, `S_(A)=ut+(1)/(2)at^(2)`
`=20xx50+0`
=1000m
For train B, `a=1m//s^(2)`
`therefore S_(B)-S_(A)=2250-1000=1250m`