Fat: The Fuel of Migrating Birds

Part A = 455.165 km

Part B = 8.9523 g

Part C = 3.1107 g

Solutions Below:

Part A

_{b}without stopping for feeding. How far will the bird fly before feeding again?

Express your answer in kilometers.

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 4 grams of fat has about 157,394 J of energy. One Watt is equal to 1 joule per second, so a bird that burns energy at a rate of 3.7 W is burning 3.7 joules a second. This means it can fly for about 42,539 seconds (157,394 / 3.7). At a speed of 10.7 m/s, it will fly for about 455,165 m, which equals 455.165 km.

455.165 km

Part B

_{carb}would the bird have to consume to travel the same distance d

_{b}?

Express your answer in grams

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 4 grams of fat during its flight, it would have to consume 2.2381 * 4 = 8.9523 grams of carbs.

8.9523 g

Part C

Express your answer in grams.

To fly 800 km will take about 20 hours (at 40km/hr). This is equal to 72,000 seconds. At a power consumption of 1.7 W, the bird will consume (1.7 * 72,000) 122,400 J of energy. Since a gram of fat contains about (9.4 Calories * 4186 J/Calorie) 39348 joules of energy, the bird will need (122,400 / 39,348) about 3.1107 grams of fat.

3.1107 g