Question

Two trains, each having a speed of 30 km/h, are headed toward each other on the same straight track. A bird that can fly 60 km/h flies off the front of one train when they are 60 km apart and heads directly for the other train. On reaching the other train it flies directly back to the first train, and so forth. Calculate the total distance the bird travels before the trains crash.

Answer 1

Answer: $d=60\ \rm km$

Explanation:

Given:

Train's speed$=30\ \rm km/h$

Bird's speed $=60\ \rm km/hr$

Distance between the trains  $=60\ \rm km$

As the two trains are moving with same velocity they will collide at a distance of 30 km. Let t be the time when they collide

$t=\dfrac{30}{30}\\t=1\ \rm hr$

so the bird will be flying with the given velocity for 1 hr before the train collide. Let d be the distance travelled by bird

$d=60\times 1\\d=60\ \rm km$