while we jump inside a high speed train why do we fall on the exact place? as train is in high speed and we are jumping so we should fall backside. but this doesn't happen why?
You keep the speed of the train during the jump. This happens because there are no forces acting on you in the horizontal direction. For example, the air around you has the same (absolute) speed as this of the train, and so it does not interact with you in the horizontal direction.