Question

Give the value for standard atmospheric pressure in each of the following units: (a) inches of mercury (b) pounds per square inch

Short answer

(a) 29.92 inHg; (b) 14.7 psi.

Step-by-step solution

Understand Standard Atmospheric Pressure

Standard atmospheric pressure, also known as one atmosphere (1 atm), is a unit of pressure defined as being equal to 101,325 Pa (Pascals). This serves as a baseline measurement for atmospheric pressure at sea level.

Convert Atmospheres to Inches of Mercury

To convert 1 atm to inches of mercury (inHg), use the conversion factor: 1 atm = 29.92 inHg. Therefore, 1 atm equals 29.92 inches of mercury.

Convert Atmospheres to Pounds per Square Inch

To convert 1 atm to pounds per square inch (psi), use the conversion factor: 1 atm = 14.7 psi. Therefore, 1 atm is equal to 14.7 pounds per square inch.

Key concepts

Conversion Factors

Conversion factors are crucial tools in the realm of physical science, especially when dealing with various units of measurement. They help us switch between units seamlessly, simplifying complex problems. For atmospheric pressure, specific conversion factors are used to express pressure in different units.

When converting standard atmospheric pressure from atmospheres (atm) to inches of mercury (inHg), you rely on a key conversion factor:

• 1 atm = 29.92 inHg

Similarly, another conversion factor helps translate atmospheres into pounds per square inch (psi):

• 1 atm = 14.7 psi

With these conversion factors, calculating equivalent values becomes straightforward, enabling a deeper understanding of pressure concepts in various contexts.

Atmospheric Pressure Units

Understanding atmospheric pressure begins with recognizing the diverse units used to measure it. The choice of units can vary based on geographical preferences and scientific applications.

Some common units include:

• Pascals (Pa): The SI (International System of Units) measurement for pressure. Defined precisely as one newton per square meter, it forms the foundation of scientific pressure calculations.
• Inches of Mercury (inHg): Predominantly used in weather reports and aviation, this unit measures pressure based on the height of a mercury column.
• Pounds per Square Inch (psi): Frequently used in engineering and tire pressure measurements. Psi ties in closely with familiar everyday applications.

Atmospheric pressure can be expressed in each of these units, making it adaptable for various fields and practical uses.

Measurement at Sea Level

Standard atmospheric pressure is most commonly referenced at sea level, providing a baseline for comparisons. This measurement takes into account the weight of the air above us, which is the greatest at sea level.

Several key points regarding measurement at sea level include:

• Sea level is the reference point: It's the foundational measurement level for atmospheric pressure, ensuring readings are consistent.
• Influence of altitude: As you ascend above sea level, atmospheric pressure decreases because there is less air above you exerting pressure.
• One Atmosphere: At sea level, the pressure is defined as one atmosphere (1 atm), equating to 101,325 Pa or 14.7 psi.

By using sea level as a standard, we achieve uniformity and consistency in pressure measurements across the globe.