Penguin huddling. To withstand the harsh weather of the Antarctic, emperor penguins huddle in groups (Fig. 18−50) . Assume that a penguin is a circular cylinder with a top surface area a=0.34m² and height h=1.1m. Let Pr be the rate at which an individual penguin radiates energy to the environment (through the top and the sides); thus NP, is the rate at which N identical, well-separated penguins radiate. If the penguins huddle closely to form a huddled cylinder with top surface area Na and height h, the cylinder radiates at the rate Ph . If N=1000, (a) what is the value of the fraction Pk/NPr and (b) by what percentage does hudding reduce the total radiation loss?
