Does a baseball fly farther in moist air or dry air?

Dear Tom,

Does a baseball fly farther in moist air or dry air?

Beth Millar,
Chicago

Dear Beth,
When a baseball flies through air, it must push aside air in its path. That uses energy that would otherwise carry the ball forward. A baseball flying in air that is more dense will lose energy more rapidly than if it were flying through less dense air, and it will therefore fall sooner. Consequently, anything that causes air to be less dense will result in the ball traveling farther. Air is less dense at higher elevations, warm air is less dense than cool air and moist air is less dense than dry air. Recall that the molecular weight of a water molecule is less than the molecular weight of nitrogen and oxygen molecules, the gases that make up 99 percent of dry air. When moisture is added to dry air, lighter water molecules displace heavier oxygen and nitrogen molecules and the air becomes less dense.

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