# What is the total distance that the bird has traveled at the moment that the two cars have reached each other?

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Consider a road with two cars at a distance of 100 kilometers which are driving towards each other. The left car drives at a speed of forty kilometers per hour and right car at a speed of sixty kilometers per hour. A bird starts from the location of right car and flies at a speed of 80 kilometers per hour. When it reaches the left car, it turns its direction, and when it reaches the right car, it turns its direction again to the opposite, etc. Check the figure for the details

Now the question is what is the total distance that the bird has traveled at the moment that the two cars have reached each other?

posted Mar 2, 2014

It is obvious that the two cars meet each other after one hour. On that moment, the bird has flown for one hour.

Conclusion: The bird has flown 80 km/h × 1 h = 80 km.

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Accidentally, two trains are running in the opposite direction and enter a tunnel that is 200 kms long. A supersonic bird that has fled the lab and taken shelter in the tunnel starts flying from one train towards the other at a speed of 1000 kmph. As soon as it reaches the second train, he starts flying back to avoid collision and meets the first train again at the other end. The bird keeps flying to and fro till the trains collide with each other.

What is the total distance that the supersonic bird has traveled till the trains collided?

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Consider four (dimensionless) flies, two males and two females. They are situated at the corners of one square meter. Every fly tries to reach the male/female fly in front of her/him. Their initial situation is visualized in the picture. Since the flies are flying towards another, they will meet each other at a certain time in the center of the square.