why does not the water fall down soon while going in train.........?

Inertial velocity and the wind resistance account for the counter-intuitive appearance of raindrops on a train or bus. There is even a physics course at Oregon State which requires that students work out the vector equation for raindrops on the rear window of a car. Weird!

http://web.engr.oregonstate.edu/~mjb/cs519/Tests/t...

For background on inertial space, take a look at:

http://en.wikipedia.org/wiki/Inertial_space

First thing, as you know, Speed = Frequency * Wavelength. Both Frequency and wavelength of the air is so much in a moving train where air is coming opposite to you that it tends to push back any mass which is not having the same Frequency back to its medium containing the normal frequency and wavelength.

Secondly , The Law of gravitation says that the gravitational force decreases as the inverse square of distance increase. When the medium between the Gravitational force and the Pouring of water increases due to push back of water by air inside the train. The Gravitational force also has not much role to play during those seconds and

Thus, the Water falls back , from where it is poured.

while going with certain speed all the things inside the train move with the same speed even the water in the bottle,when u r pouring the water it have moment of inertia which make it be slowly when the water transfer from the the bottle to the glass into air.

If the train is moving with constant speed, all objects in it are moving with constant speed.

In that circumstance, every thing inside the train will behave as if the train were rest.

But during acceleration or deceleration the things will be different.

Newton Firt LAw

because the water is not moving with the train so it will hit the nearest objet next to it and it just so happen that the backseat is nearer than the floor