Question

A person eats a dessert that contains 250 Calories. (This "Calorie" unit, with a capital C, is the one used by nutritionists; 1 Calorie=4186 J.) The skin temperature of the perosn is 37 degrees C and that of her environment is 22 degrees C. The emissivity of her skin is 0.77 and its surface area is 1.3M^2. How many hours would it take her to emit a net radiant energy from her boyd that is equal to the energy contained in this dessert?

Answer 1

From Stefan Boltzmann law we have, Net thermal energy radi ated is given by or But given that pt 250x4186 J 1046500 J 1046500 J 0.77 x5.67x10-s watt-m-2-K+,13m,水310K-(295 K)4 ) -11095.01s -2.83 hours Hence, time taken to emit a net radi ant energy equal to the energy containedin the desert is 2.83 hours