Small birds can migrate over long distances without feeding, storing energy most

Question

Small birds can migrate over long distances without feeding, storing energy mostly as fat rather than carbohydrate. Fat is a good form of energy storage because it provides the most energy per unit mass: 1 gram of fat provides about 9.4 (food) Calories, compared to 4.2 (food) Calories per 1 gram of carbohydrate. Remember that Calories associated with food, which are always capitalized, are not exactly the same as calories used in physics or chemistry, even though they have the same name. More specifically, one food Calorie is equal to 1000 calories of mechanical work or 4186 joules. Therefore, in this problem use the conversion factor 1 calorie = 4186 J.

Consider a bird that flies at an average speed of 10.7 and releases energy from its body fat reserves at an average rate of 3.70 (this rate represents the power consumption of the bird). Assume that the bird consumes of fat to fly over a distance without stopping for feeding. How far will the bird fly before feeding again? Express your answer in kilometers.

How many grams of carbohydrate would the bird have to consume to travel the same distance ? Express your answer in grams

Explanation / Answer

(a) 4g of fat = 4*9.4 food cal = 37.6 food cal = 37.6*4186 = 157,393 J Time it can fly = 157393/3.70 = 42539 s Distance it can fly = 42539*10.7 = 455,165 m = 455.165 km (b) 37.6 food cal = 37.6/4.2 = 8.95 Carbohydrates

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