while travelling in a bus or train, air comes inside the vehicle but it seems it goes nowhere I have been amazed observing that while travelling in a train or bus , we feel air comming into the vehicle. I know this is due to difference in pressure but my question is that we dont feel air going out of it. is this fact true? where do the incomming air go and how?
 A: If air comes into the vehicle then it must effectively also be leaving it, otherwise pressure would be building up, in accordance with the Ideal Gas Law.
Trains and buses are hardly hermetically sealed containers. The reason why you may not notice the air leaving is that it will flow through many orifices like imperfect seals, a slightly open window further down from where you sit and other vents. This makes the leaving air flow divided into many smaller streams, which are harder to notice.
A: Have you ever blown out a candle, from a few inches away?
Have you ever wondered why you can't suck out a candle from the same distance?
The motion of fluids like air, through an orifice, is not reversible.
On the side where it is leaving the orifice it forms a localized stream, which you feel.
On the side where it is entering the orifice it comes from all directions, so you don't feel it.
The wind is coming in some windows and going out others, but you only feel it where it is coming in because it is in a concentrated stream.
