Help with part A and B Fat: The Fuel of Migrating Birds - MC Part A Consider a b

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Help with part A and B

Fat: The Fuel of Migrating Birds - MC Part A Consider a bird that flies at an average speed of 10.1 m/s and releases energy from its body fat reserves at an average rate of 3.50 Watt (this rate represents the power consumption of the bird). Assume that the bird consumes 3.2 g of fat to fly over a distance db without stopping for feeding. How far will the bird fly before feeding again? Small birds like that in (Figure 1) 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 per unit mass: 1.00 grams of fat provides about 9.40 (food) Calories, compared to 4.20 (food) Calories per 1.00 grams 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 provides the most energy Express your answer in kilometers using three significant figures Hints km Figure 1 Submit My Answers Give Up of 1 Part B How many grams of carbohydrate mcarb would the bird have to consume to travel the same distance db? Express your answer in grams using three significant figures Hints Submit My Answers Give Up

Explanation / Answer

1) The problem tells us that one gram of fat has 9.4 Calories. Each Calorie equals 4186 J, so that means a gram of fat contains about 39,348 J of energy, and 3.2 grams of fat has about 125913.6 J of energy.

One Watt is equal to 1 joule per second, so a bird that burns energy at a rate of 3.5 W is burning 3.5 joules a second. This means it can fly for about 35975.3 seconds (125913.6/ 3.5).

At a speed of 10.1 m/s, it will fly for about 363350.7 m, which equals 363.35 km.

2) The problem tells you that one gram of fat has about 9.4 Calories of energy, compared to 4.2 for a gram of carbs. So there is 2.2381 times as much energy in a gram of fat.

If the bird consumes 3.2 grams of fat during its flight, it would have to consume 2.2381 * 3.2 = 7.162 grams of carbs.

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