Question

why does we have to sun a certain distance in the direction of motionof a train while stopping out?​

Answer 1

Its advised to not to stand near a running train because at that time the velocity / speed of the train is high and creates a lower pressured region around the moving train thus there are possibility that the person near that region could be pulled into the moving train which causes physical injuries and might get too risky to be in that place thus its prefered for passengers and common people to maintain some distance with a moving train.