Chapter 13, Problem 72PP

Elephants under pressure. An elephant can swim or walk with its chest several meters underwater while the animal breathes through its trunk, which remains above the water surface and acts like a snorkel. The elephant’s tissues are at an increased pressure due to the surrounding water, but the lungs are at atmospheric pressure because they are connected to the air through the trunk. Figure 13.47 shows the gauge pressures in an elephant’s lungs and abdomen when the elephant’s chest is submerged to a particular depth in a lake. In this situation, the elephant’s diaphragm, which separates the lungs from the abdomen, must maintain the difference in pressure between the lungs and the abdomen. The diaphragm of an elephant is typically 3.0 cm thick and 120 cm in diameter.

Figure 13.47

Problems 70–73.

72. How does the force the diaphragm experiences due to the difference in pressure between the lungs and abdomen depend on the abdomen’s distance below the water surface? The force

1. A.    increases linearly with distance.
2. B.     increases as distance squared.
3. C.     increases as distance cubed.
4. D.    increases exponentially with distance.