Concept: A barometer measures atmospheric pressure, which is the force exerted by air above a surface.
Explanation: Atmospheric pressure is the weight of a column of air per unit area on Earth’s surface.
A barometer, often using mercury, shows this pressure by the height of the mercury column.
The pressure
Pa equals
ρgh, where
ρ is mercury’s density,
g is gravity, and
h is the column height.
This instrument does not measure rainfall, temperature, or sea level directly.
Thus, its primary use is to read atmospheric pressure.
Answer: C. measure atmospheric pressure
