AAMC FL Practice Exam

What is the total work generated by a healthy adult circulating 9 L of blood in 10 minutes?

1. 60 kJ

2. 120 kJ

3. 180 kJ

4. 240 kJ

The correct answer is: 120 kJ

To determine the total work generated by a healthy adult circulating 9 L of blood in 10 minutes, it's essential to consider the relationship between blood flow, pressure, and work. The work done by the heart can be calculated using the formula: Work = Volume x Pressure In this case, we know the volume of blood being circulated is 9 liters. To convert this volume into a more standard unit for work calculations, we convert liters to milliliters (1 L = 1000 mL), resulting in 9000 mL. For the pressure, a typical value for mean arterial pressure in a healthy adult is around 80 mmHg, which can be converted into pascals (1 mmHg = 133.32 Pa), yielding: 80 mmHg * 133.32 Pa/mmHg = approximately 10665.6 Pa. Now, we calculate the work done in joules using these figures: Work = 9000 mL x 10665.6 Pa (since 1 mL = 1 x 10^-6 m³, we include this conversion into our calculations) This leads to a total energy expenditure that can be converted into kilojoules. In this context, the