Two trains, each having a speed of s, are headed at each other on the same straight track. A bird that can fly at speed 2s flies off the front of one train when they are d apart and heads directly for the other train. On reaching the other train it flies directly back to the first train, and so forth. (We have no idea why a bird would behave in this way.) In terms of variables given in the problem, what is the total distance the bird travels?

The total distance the bird travels is d.

Explanation:

Each train travels at the speed s. They will meet at the center, a distance d/2 (which is where the bird might be crushed). Each train travels the same distance d/2 in a time t which is also equal for both. This is also the time the bird spends travelling between them.

For any of the train, the time t is the distance divided by the speed.

The bird travels at the speed of 2s. Its distance is given by the product of its speed and the time taken.

the area between the graph and the t axis

answer(20) psi;