Question

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

Answer 1

Initially,

Relative Acceleration a = 1 ms^-2

v₀ = 72 kmh^-1 = 72 × (5/18) ms^-1

= 20 ms^-1

Relative displacement = x

Relative velocity initially = V₀ – V₀ = 0

X = 1/2 at²

= 1/2 × 1 × 50² = 1250 m

Original distance between the trains = 1250 m.

Answer 2

Let s= distance between the trains initially

Velocity of trains initially

velocity of train B w.r.t. A is zero, acceleration of train B w.r.t. A  is 

a=1ms⁻²

Then distance