Question

A person getting out of a moving bus on a train falls in froward direction.

Answer 1

This is the same reason that the same person who is standing leans toward when a bus stops,

leans left or right when a bus turns Orleans back when a bus accelerates. This is all due to inertia.

You are moving you are going to go the same direction as you were in the bus.

Basically the law of inertia states when an object is at rest stays at rest

and an object in motion stays in motion until an outside force is acted upon that object.

Because of this you are moving with the bus until your feet touch the ground and the ground

along with your muscles prevent you from moving.