Physics Homework Help

Posted on 2014-04-01 07:21:00 in Physics by ANONYMOUS

1.) In the conduction equation Q = (kA?T)t/L, the combination of factors kA/L is called the conductance. The human body has the ability to vary the conductance of the tissue beneath the skin by means of vasoconstriction and vasodilation, in which the flow of blood to the veins and capillaries underlying the skin is decreased and increased, respectively. The conductance can be adjusted over a range such that the tissue beneath the skin is equivalent to a thickness of 0.088 mm of Styrofoam or 3.6 mm of air. By what factor can the body adjust the conductance?



2.) A person eats a dessert that contains 210 Calories. (This "Calorie" unit, with a capital C, is the one used by nutritionists; 1 Calorie = 4186 J.) The skin temperature of this individual is 36°C and that of her environment is 17° C. The emissivity of her skin is 0.75 and its surface area is 1.3 m2. How much time would it take for her to emit a net radiant energy from her body that is equal to the energy contained in this dessert?

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