Question

An agricultural worker expired 150 litres of air having 16% oxygen in 5 minute duration. What is the oxygen consumption in litre per minute to perform the activity?

• A. 30.0
• B. 4.0
• C. 3.0
• D. 1.5

Hint:

Always assume the standard atmospheric oxygen concentration is \(21%\) for inhaled air.
The difference between inhaled and exhaled oxygen concentrations (typically \(5%\)) represents the proportion of oxygen absorbed by the body.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Ergonomics and human work science evaluate energy expenditure during physical activities.
We can determine this by measuring the rate at which the body consumes oxygen during respiration.
Key Formula or Approach:
The rate of oxygen consumption (\(\text{VO}_2\)) is calculated as: \[ \text{VO}_2 = \text{Ventilation Rate} \times (% \text{ Oxygen Inhaled} - % \text{ Oxygen Exhaled}) \] where:
- The standard concentration of oxygen in inhaled atmospheric air is \(21%\) (or \(0.21\)).
- The concentration of oxygen in expired air is given as \(16%\) (or \(0.16\)).

Step 2: Detailed Explanation:
Let's list the given parameters:
- Total volume of air expired = \(150 \text{ Litres}\)
- Duration of activity = \(5 \text{ minutes}\)
First, calculate the ventilation rate (the volume of air breathed per minute): \[ \text{Ventilation Rate} = \frac{150 \text{ Litres}}{5 \text{ minutes}} = 30 \text{ L/min} \] Next, determine the percentage of oxygen absorbed by the lungs: \[ % \text{ Oxygen Consumed} = 21% - 16% = 5% \] Now, calculate the absolute rate of oxygen consumption: \[ \text{Oxygen Consumption Rate} = 30 \text{ L/min} \times \frac{5}{100} = 1.5 \text{ L/min} \]

Step 3: Final Answer:
The worker's oxygen consumption rate is 1.5 litres per minute.