Question

A balloon filled with hydrogen gas rises up into the air due to ______ force exerted on it by the atmospheric air.

Answer 1

1. Buoyancy is the property of a fluid to exert an upward force on an object immersed in it.
2. The atmospheric air is the fluid and the hydrogen balloon is the object. Atmospheric air exerts buoyant force on the hydrogen balloon.

Hence, a balloon filled with hydrogen gas rises up into the air due to buoyant force exerted on it by the atmospheric air.