Physics

Physics, 28.08.2019 19:30, KrishnaBalaram1235

The ceiling of a single-family dwelling in a cold climate should have an r-value of 46 ft2 ·f°·h/btu. to give such insulation, how thick would a layer of (a) polyurethane foam and (b) silver have to be? the thermal conductivity of polyurethane foam is 0.024 w/m·k, and the thermal conductivity of silver is 428 w/m·k.

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Physics, 24.06.2019 16:50, lrasanaoaksandfurana

Animals in cold climates often depend on two layers of insulation: a layer of body fat [of thermal conductivity 0.200w/(m⋅k) ] surrounded by a layer of air trapped inside fur or down. we can model a black bear (ursus americanus) as a sphere 1.60m in diameter having a layer of fat 3.90cm thick. (actually, the thickness varies with the season, but we are interested in hibernation, when the fat layer is thickest.) in studies of bear hibernation, it was found that the outer surface layer of the fur is at 2.80∘c during hibernation, while the inner surface of the fat layer is at 30.9∘c a) what should the temperature at the fat-inner fur boundary be so that the bear loses heat at a rate of 51.4w ? b) how thick should the air layer (contained within the fur) be so that the bear loses heat at a rate of 51.4w ?

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Physics, 05.07.2019 19:20, chitteshchandra56

Animals in cold climates often depend on two layers of insulation: a layer of body fat [of thermal conductivity 0.200w/(m⋅k) ] surrounded by a layer of air trapped inside fur or down. we can model a black bear (ursus americanus) as a sphere 1.60m in diameter having a layer of fat 3.90cm thick. (actually, the thickness varies with the season, but we are interested in hibernation, when the fat layer is thickest.) in studies of bear hibernation, it was found that the outer surface layer of the fur is at 2.80∘c during hibernation, while the inner surface of the fat layer is at 30.9∘c a) what should the temperature at the fat-inner fur boundary be so that the bear loses heat at a rate of 51.4w ? b) how thick should the air layer (contained within the fur) be so that the bear loses heat at a rate of 51.4w ?

Answers: 3

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Physics, 31.07.2019 02:20, nevelle

Animals in cold climates often depend on two layers of insulation: a layer of body fat [of thermal conductivity 0.200 w/(m⋅k) ] surrounded by a layer of air trapped inside fur or down. we can model a black bear (ursus americanus) as a sphere 1.50 m in diameter having a layer of fat 3.90 cm thick. (actually, the thickness varies with the season, but we are interested in hibernation, when the fat layer is thickest.) in studies of bear hibernation, it was found that the outer surface layer of the fur is at 2.70 ∘c during hibernation, while the inner surface of the fat layer is at 31.3 ∘c. assume the surface area of each layer is constant and given by the surface area of the spherical model constructed for the black bear. what should the temperature at the fat-inner fur boundary be so that the bear loses heat at a rate of 50.8 {\rm w}? how thick should the air layer (contained within the fur) be so that the bear loses heat at a rate of 50.8 {\rm w}?

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