Weight of 1 cc of air at normal pressure and temperature
**Core Concept:**
Weight of a substance is the force exerted by it due to gravity. In this case, we are considering the weight of air at normal pressure and temperature. The density of air is approximately 1.2 kg/m³ or 1200 kg/m³ (1200 grams per cubic meter), and the acceleration due to gravity is approximately 9.8 m/s². To find the weight of 1 cc of air, we need to multiply its density by the acceleration due to gravity.
**Why the Correct Answer is Right:**
The correct answer (D) is obtained by multiplying the density of air (1200 kg/m³) by the acceleration due to gravity (9.8 m/s²). This gives us the weight of 1 cc of air:
**Correct Answer: 1200 kg/m³ * 9.8 m/s² = 11,760 kg m/s²**
**Why Each Wrong Option is Incorrect:**
A) and B) are incorrect because they do not consider the density of air (1200 kg/m³) in their calculation.
C) is incorrect because it assumes a different density for air (e.g., 1 kg/m³), which is incorrect for normal atmospheric conditions.
**Clinical Pearl:**
The weight of a substance like air is significant in certain medical contexts, especially in the calculation of respiratory rate (RR) and oxygen saturation (SpO2) measurements in critically ill patients. For example, when assessing respiratory rate, knowing the weight of air can help calculate the volume of air inhaled or exhaled per minute. Additionally, understanding the weight of air is essential for calculating oxygen saturation, which is a critical parameter in monitoring a patient's respiratory status.