Q. 17 Molecules in the air in the atmosphere are attracted by the gravitational force of the earth. Explain why all of them do not fall into the earth just like an apple falling from a tree.
Hint: The motion of the air molecules merely depends on the gravitational force.
Air molecules in the atmosphere are attracted vertically downward by the gravitational force of the earth just like an apple falling from a tree. Air molecules move randomly due to their thermal velocity and hence the resultant motion of air molecules is not exactly in the vertically downward direction. But in the case of apple, only vertical motion dominates because of being heavier than air molecules. But due to gravity, the density of the atmosphere increases near to the earth's surface.
