two trains A and B of length 400m each are moving on two parallel tracks with a uniform speed of - Physics - Motion In A Straight Line

Question

two trains A and B of length 400m each are moving on two
parallel tracks with a uniform speed of 72 km/h in the same
direction,with A ahead of B The driver of B decides to overtake A
andaccelerates by 1m/s^2 If after 50s ,the guard of B just
brushes past the driver of A,what was the original distance between
them?

Shrimali · Answer

The correct answer is 450 m

Here is my explanation

Using concept of relative velocity,

u = 0 (both the trains have same velocity); S = x(i e original
distance between the trains) + 2*400(the train B will also have to
travel the length of its own and also the length of the train
A)

Using second equation of motion,

S = ut + 1/2 at^2

=> x + 800 = 1/2 * 1 * 2500 = 1250 m

=> x = 450 m

Thus the original distance between the trains should be 450
m
Hope that it helps
Thanks