Which phrase best describes air pressure?

• A. The force exerted per unit area by air molecules on a surface ($P=\frac{F}{A}$)
• B. The temperature of the air ($T$)
• C. The speed at which air molecules move ($v$)
• D. The total mass of air in a given volume ($m/V$)

Answer: (A)

Verified step by step guidance

1. Understand that air pressure is a physical quantity that describes how air molecules interact with surfaces.
2. Recall that pressure is defined as the force applied perpendicular to a surface divided by the area of that surface.
3. Express this relationship mathematically as \(P = \frac{F}{A}\), where \(P\) is pressure, \(F\) is the force exerted by air molecules, and \(A\) is the area over which the force is distributed.
4. Recognize that temperature (\(T\)), speed of air molecules (\(v\)), and mass per volume (\(\frac{m}{V}\)) describe other properties of air, such as thermal energy, molecular motion, and density, but do not directly define pressure.
5. Therefore, the phrase that best describes air pressure is 'The force exerted per unit area by air molecules on a surface.'