Air pressure
ScienceDefinition
Air pressure (atmospheric pressure) is the force exerted by the weight of air molecules in the atmosphere on a given surface area. It decreases with increasing altitude because there is less air above pushing down, and it varies with temperature and humidity.
Examples
- Standard atmospheric pressure at sea level is 101.325 kPa (1 atm or 760 mmHg)
- Your ears pop on an airplane because the air pressure inside your ear differs from the lower cabin pressure at altitude
- Barometers measure air pressure to help predict weather—falling pressure often signals approaching storms
Key Fact
1 atm = 101,325 Pa = 760 mmHg = 14.7 psi at sea level.
Study This Concept
Practice air pressure with free review games in these units: