How are the air velocities determined by an anemometer?

An anemometer measures air velocity by determining the linear footage of air that passes through a given area, and this information is typically reflected on dials connected to the device. The mechanism works on the principle that as air moves, it drives the anemometer's rotating components. The speed of these rotations corresponds to the velocity of the air movement. The dials provide a direct correlation to the distance traveled by the air in terms of linear feet, translating that movement into velocity readings for meaningful interpretation.

The other options focus on different aspects of air dynamics. Counting the number of rotations could provide some data, but it does not directly capture the measurement of air velocity in a linear sense. Assessing temperature changes relates more to thermodynamics and environmental conditions rather than direct airflow measurement. Evaluating the pressure differential in the air may give insights into airflow but does not directly yield velocity readings obtained by the anemometer’s primary function. Thus, measuring the air travel in linear feet is the most accurate and applicable method for determining air velocity with this instrument.