4. On a clear day, 3.4 W of radiation from the sun is absorbed by a leaf that has an area of 40 cm² and a mass of 0.45 grams. Let the leaf have a specific heat capacity of 0.8 cal/g-C, and an emissivity of 0.8 (A) How fast do you calculate the temperature of the leaf is rising from this information? (B) What temperature would the leaf reach if it only lost heat through radiation to 20 C surroundings. (C) Why won't it get as high as your estimate in (B) in reality? 5. Hypothermia sets in when normal body temperature of 37C falls to 35C. Suppose a person is losing 200 W and metabolism is only providing 80 W. (A) How long will it take a person of 70 kg mass to reach hypothermia. ? We'll take the person's specific heat capacity as that of water. (B) Let's suppose the heat loss is through a goose down parka. Goose down is a good insulator because it is mostly air. So is snow! So, further let's imagine the person is awaiting a rescue in an arctic expedition and from the above calculation, they realize that rescue will take twice as long as it will likely take to reach hypothermia. How can they use a layer of snow to stave of the onset of hypothermia? Can you relate thickness of snow to anything else?

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