The atmospheric pressure is usually measured in the unit of :

Options

A. newtons per square metre
B. pascal
C. cm of mercury
D. mm of mercury

Answer

To solve the question regarding the unit in which atmospheric pressure is usually measured, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Atmospheric Pressure**:
- Atmospheric pressure is the force exerted by the weight of air above a surface. It is an important concept in physics and meteorology.

2. **Identify the Units of Pressure**:
- The question provides four options:
- Newton per square meter (N/m²)
- Pascals (Pa)
- Centimeters of mercury (cmHg)
- Millimeters of mercury (mmHg)

3. **Recognize Common Units of Pressure**:
- Newton per square meter (N/m²) and Pascals (Pa) are both units of pressure, with 1 Pascal being equivalent to 1 N/m².
- Centimeters of mercury (cmHg) and millimeters of mercury (mmHg) are also units used to measure pressure, particularly in barometric measurements.

4. **Determine the Standard Measurement for Atmospheric Pressure**:
- Atmospheric pressure is commonly measured using a barometer. The standard atmospheric pressure at sea level is defined as 760 mmHg.

5. **Select the Correct Answer**:
- Since the question asks for the unit in which atmospheric pressure is usually measured, the correct answer is **millimeters of mercury (mmHg)**.

### Final Answer:
The atmospheric pressure is usually measured in the unit of **millimeters of mercury (mmHg)**.

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