Will a baseball travel faster in cold air or warm air?

Answer 1

Excerpt Taken From Washington Post Article by Ann Posegate, October 2, 2008

http://voices.washingtonpost.com/capitalweathergang/2008/10/weather_and_baseball.html

Humidity

High humidity actually yields air that is less dense, thus providing less air resistance for a traveling ball and allowing it to go further. This is an interesting and counterintuitive fact due to water vapor being lighter (in mass) than oxygen and nitrogen in air. Taking it back to high school chemistry, density equals mass over volume. The more water vapor that's present in the air, the lighter and less resistant the air is.

Temperature

Air expands as it warms. So warm air is less dense -- there's more space between the air molecules -- than cold air. Warm temperatures therefore also help a ball to travel a bit farther.