Question

What should be the speed of practically calm wind?

• A. \(1\text{ km / hr}\)
• B. \(3\text{ km / hr}\)
• C. \(5\text{ km / hr}\)
• D. \(9\text{ km / hr}\)

Hint:

In animal housing, calm wind conditions (\(< 2\text{ km/hr}\)) during hot, humid summers can lead to heat stress. An air speed of \(3\) to \(5\text{ km/hr}\) is ideal for natural cooling inside sheds.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
In agricultural bioclimatology and meteorology, wind speed is classified using standard indexes, such as the Beaufort Wind Scale.

Step 2: Detailed Explanation:
According to the Beaufort Wind Scale:
- Force 0 (Calm): Wind speed is under \(1\text{ knot}\) (less than \(1.85\text{ km/hr}\)), practically measured as \(0\) to \(1\text{ km/hr}\). Under these conditions, smoke rises straight up, and leaves are completely still.
- Force 1 (Light Air): Wind speed is \(1\) to \(5\text{ knots}\) (\(2\) to \(9\text{ km/hr}\)). Smoke drifts slightly, but wind vanes do not move.
- Force 2 (Light Breeze): Wind speed is \(6\) to \(11\text{ knots}\) (\(10\) to \(19\text{ km/hr}\)). Wind can be felt on the skin, and leaves rustle.
Therefore, a wind speed of \(1\text{ km/hr}\) represents practically calm conditions.

Step 3: Final Answer:
The speed of practically calm wind is \(1\text{ km / hr}\).