Question

6. Two trains A and B, each of length 400 m, are
eq.
moving on two parallel tracks with a uniform speed of
72 km h in the same direction, A being ahead of B.
The driver of B decides to overtake A and accelerates bus
by 1 m s-. After 50 s, the guard (end-point) of B just min
moves past the driver (front-point) of A. What was the
original distance between the two trains ?
Please give me answer ​

Answer 1

Answer : 450m

Explanation:

✓ In a frame moving parallel to the two trains with same velocity 72kmph, both the trains appear to be at rest. Now, the train B accelerates through 1m/s^2 to cover a net distance equivalent to the two train's length + the distance between the two trains.

✓ Assuming the distance is l, acceleration a, time taken to just overtake A is t :

$400 \times 2 + l = \frac{1}{2} a {t}^{2}$

$l = \frac{1}{2} (1) {(50)}^{2} - 800 = 450m$