Chapter 15, Problem 20CQ

Think about the drinking bird at the beginning of this section (Figure 15.21). Although the bird enjoys the theoretical maximum efficiency possible, it left to its own devices ever time, the bird will cease “drinking." What are some of the dissipative processes that might cause the bird's motion to cease?

Figure 15.21 This novelty toy, known as the drinking bird, IS an example of Carnot's engine. It contains methylene chloride (mixed with a dye) in the abdomen, which boils at a very low temperature—about 100°F. To operate, one gets the bird's head wet. As the water evaporates, fluid moves up into the head, causing the bird to become top-heavy and dip forward back into the water. This cools down the methylene chloride in the head, and it moves back into the abdomen, causing the bird to become bottom heavy and tip up. Except for a very small Input of energy—the original head- wetting—the bird becomes a perpetual motion machine of sorts. (credit: Arabesk.nl, Wikimedia Commons)