How does atmospheric pressure change with height and the basic cause?

How does atmospheric pressure change with height and the basic cause?

• A. Pressure increases with height due to more air above pushing down; density rises with altitude
• B. Pressure remains constant with height; only temperature changes
• C. Pressure fluctuates randomly with height; not related to air above
• D. Pressure decreases with height because less air above pushing down; density and pressure fall off with altitude

Answer: (D)

The main idea is that atmospheric pressure is the weight of the air above a point, so it decreases as you go higher. The atmosphere is in hydrostatic balance, meaning pressure changes with height according to how much air mass sits above: as you rise, there’s less air above you to push down, so the pressure drops. This is described by a relation where the pressure gradient is negative with height (dP/dz = -ρg), so pressure falls off roughly exponentially with altitude. Because pressure and density are tied together by the gas behavior of air, lower pressure at higher elevations also means lower density—the air is thinner there. Temperature influences this too, but the overarching cause is gravity creating a weight of air above each layer; less air above at higher levels equals lower pressure and lower density.

The main idea is that atmospheric pressure is the weight of the air above a point, so it decreases as you go higher. The atmosphere is in hydrostatic balance, meaning pressure changes with height according to how much air mass sits above: as you rise, there’s less air above you to push down, so the pressure drops. This is described by a relation where the pressure gradient is negative with height (dP/dz = -ρg), so pressure falls off roughly exponentially with altitude.

Because pressure and density are tied together by the gas behavior of air, lower pressure at higher elevations also means lower density—the air is thinner there. Temperature influences this too, but the overarching cause is gravity creating a weight of air above each layer; less air above at higher levels equals lower pressure and lower density.