The velocity of wind is measured by

The correct answer is B) Anemometer. It measures wind speed, which is the velocity component of wind. Cup and vane-type anemometers are standard at IMD observatories, and the reading is usually given in km/h or m/s.

• Barometer (A) measures atmospheric pressure, not wind speed. Its readings help forecasters track pressure systems, cyclones and fronts.
• Hydrometer (C) measures the relative density or specific gravity of liquids, such as battery acid or milk. It has nothing to do with air movement.
• Wind Vane (D) shows the direction from which wind blows, not its speed. It is paired with an anemometer at weather stations.

The core concept is the set of instruments used in meteorological observation, which is part of the Physical Geography syllabus under atmospheric circulation and weather. For Mains, the link is to disaster management and early warning systems, where wind speed and direction both matter for cyclone forecasting.

Trap: Aspirants often confuse the wind vane with the anemometer because both are seen together at weather stations. Remember that the vane gives direction and the anemometer gives speed.