Question

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 driver of B decides to overtake A and accelerates by 1 m/s². If after 50 s, the guard of B just brushes past the driver of A, what was the original distance between them?

Answer 1

For train A:​

Initial velocity, u = 72 km/h = 20 m/s
Time, t = 50 s
Acceleration, a_I = 0 (Since it is moving with a uniform velocity)
From second equation of motion, distance (sI) covered by train A can be obtained as:

For train B:
Initial velocity, u = 72 km/h = 20 m/s
Acceleration, a = 1 m/s²
Time, t = 50 s

From second equation of motion, distance (s_II) covered by train A can be obtained as:

Hence, the original distance between the driver of train A and the guard of train B = 2250 –1000 = 1250 m.