Question

Two trains of equal lengths are running on parallel tracks in the same direction at 85 km/h and 71 km/h, respectively. the faster train passes the slower train in 40 sec. the length of each train is

Answer 1

Concept:

(i) When two trains pass to each other then total length will be the sum of the lengths two trains.

(ii) When two trains move in the same direction then their relative speed will be equal to the difference of their speeds.

Given: Length of two trains are equal.

Speed of faster train (v₁) = 85 km /h = 85 × (5/18) m/s

Speed of slower train (v₂) = 71 km /h = 71 × (5/18) m/s

Their passing time (t) = 40 s.

Let 'L' be the length of each train.

Apply the formula for speed,

Relative Speed = Total Distance / Time

(v₁ -v₂) = (L + L) / t

or, (85 -71)× (5/18) m/s = 2 L / (40 s)

or, 2 L = 1400 / 9 m

or, L = (1400 / 18) m

or, L = 77.78 m

Hence, the length of each train will be 77.78 m