Question

A 175 m long train is travelling along a straight track with a velocity 72 $k{m}^{-1}$ h. A bird is flying parallel to the train in the opposite direction with a velocity 18 $k{m}^{-1}$ h. The time taken by the bird to cross the train is :

• A. 35 s
• B. 27 s
• C. 11.6 s
• D. 7 s

Answer 1

The correct option is D 7 s

Given,

Length of train$=175m$

Velocity of bird$=18kmph$

Velocity of train$=72kmph$

Taking everything relative to train.

Velocity of bird with respect to train$=18+72=90kmph=25m{s}^{-1}$

Length to be covered by bird wrt train to cross the train$=175m$

$t=\frac{s}{v}=\frac{175}{25}=7$

$t=7s$

Option $\text{D}$ is the correct answer